First of all, please realize that you do not need to study and memorize this material. As you analyze texts, you will find "so" and "for" used as conjunctions and probably reach the conclusions described on the "Conjunctions" page on your own. The words are, however, a matter of debate among grammarians, so the following is a justification, not an explanation, of the KISS approach toward them.

"So"

     Although many modern grammarians simply consider "so" as a coordinating conjunction, the primary justification for considering it as either coordinating or subordinating is the question of meaning. Whereas coordination implies a union of -- or a choice among -- identities of equal value, the logical relationship implied by "so" is cause/effect. Most grammarians, even Paul Roberts, my favorite, ignore the question of meaning. In his discussion of "so," he claims that it is a coordinating conjunction primarily because it "must always stand between the two elements joined." (Understanding Grammar, 232-3) In other words, because "we cannot say ... 'I so gave him an order,'" so "so" cannot be a subordinating conjunction. 
     But in the same paragraph Roberts suddenly introduces the question of meaning -- "with other meanings most of these conjunction forms may function as other parts of speech," and gives the single example "'We left early so we could get some sleep' (subordinating conjunction, equal 'so that')." He never distinguishes this meaning of "so" from that of "so" as a coordinating conjunction. Who is to decide when "so" means just "so," and when it means "so that"?  It seems clear that the "so" clause in the example expresses purpose, a typical function of an adverbial clause, but Roberts' only other example of "so" is as a coordinating conjunction: "Murphy was out of cigarettes, so he strolled downtown to buy some." But this "so" clause clearly expresses "result," another typical function of adverbial clauses.
     Punctuation, according to Roberts, is irrelevant:

     Note that punctuation plays no part in the preceding analysis. There seems to be a widespread disposition to call so, for example, a conjunction because we put a comma before it, or to call it a conjunctive adverb because we put a semicolon before it. But this gets the cart before the horse. It isn't a conjunction because we use a comma, though we often use a comma because it is a conjunction. But it would still be a conjunction if we always used a semicolon or a period. (232-33)

     The difference in the way "so" is used might be a good topic for a research paper. Less mature writers may use the period and capital letter because they are unable to chunk the entire structure in short-term memory. More mature writers are probably more likely to use "so" as a subordinate conjunction, but they still have the option of breaking the sentence in two, thereby creating a short sentence for emphasis.
     Because ". So ..." functions as a coordinating conjunction, I would not argue with someone who wanted to consider it as coordinating in "He wanted candy, so I gave him some." The argument is not worth the time spent on it. We can also expect to see sentences such as "He wanted candy, and so I gave him some." In such cases, we can explain the "so" as the equivalent of  "as a result" -- "He wanted candy, and as a result I gave him some." This could be considered as incomplete subordination, but I would never consider it to be an error. (See the opening of Tom Sawyer.)

"For"

      Some grammarians consider "for" as a simple coordinating conjunction, comparable to "and," "or," and "but." You can look up their explanations and reasons on your own, but I would suggest that they have a perspective that is fundamentally different from our own. In Understanding Grammar, for example, Paul Roberts includes "for," "yet," and "so" among the coordinating conjunctions. He explains:

Because for, yet, and so never connect anything but clauses, grammarians are often dubious about calling them coördinating conjunctions. But there is no real difficulty. And, but, or, nor, for, yet, and so are to be put together because they have a syntactical peculiarity not shared by subordinating conjunctions or conjunctive adverbs: they must always stand between the two elements joined. Subordinating conjunctions must always come at the beginning of one element, but not necessarily between the two. Let us compare the coördinating conjunction for and the subordinating conjunction because:

We knew spring was coming, for we had seen a robin.
We knew spring was coming, because we had seen a robin.

Here they both stand between the clauses. But we can transpose the because clause:

Because we had seen a robin, we knew spring was coming.

We cannot, however, transpose the for clause and say, "For we had seen a robin, we knew spring was coming." (232-233)

Berlin, Isaiah:

But if that was Marx's true goal, it was not destined to be realised in the industrial countries which he designated as the theatre of the revolution. For here a fatal dilemma raises its terrible horns: if it is only on the expanding base of increasingly efficient productivity that a rational socialist system can be built, as every social democrat, reasonably enough, insisted over and over again, it would neither need, nor be likely to issue from, a revolution; this was not the climate in which revolutionary forces throve.
(Isaiah Berlin, "Marxism in the Nineteenth Century," 155)

He [Bakunin] therefore viewed Marx's conception of an orderly party as itself fatally bourgeois in spirit; for solid, serious, intelligent workers, with families and regular employment, organised into a tidy, efficiently functioning party machine under proper intellectual leadership (Bakunin's 'pedantocracy'), would surely think twice before they set out to destroy a society which, after all, had made it possible for them to attain to the level of education, organisation, prosperity and above all respectability which alone had made them politically effective.
(Isaiah Berlin, "Marxism in the Nineteenth Century," 158)

If we alone are the authors of the values, then what matters is our inner state -- motive, not consequence. For we cannot guarantee consequences: they are part of the natural world, the world of cause and effect, of necessity, not of the world of freedom.
(Isaiah Berlin, "The Romantic Revolution," 185)

Knowledge may not be a moral value at all, even though no philosopher after Plato made this denial. For it is possible to know all that is knowable, and yet to embrace evil if one is so minded: if man were not free to choose evil, he would not be truly free, creation would become a quasi-mechanical self-propulsion along the tramlines of infallible omniscience, harmonious and frictionless, but not consistent with choice or freedom.
(Isaiah Berlin, "The Romantic Revolution," 186)

The marvelous new militancy, which has engulfed the Negro community, must not lead us to a distrust of all white people. For many of our white brothers, as evidenced by their presence here today, have come to realize that their destiny is tied up with our destiny.
(Martin Luther King Jr., "I Have a Dream," as quoted in Reinking, James A. et al., Strategies for Successful Writing. fourth edition, Prentice Hall, 1996.527.)

     The use of "For" to begin sentences appears to be a matter of personal style. In his translation of Mircea Eliade's The Sacred and the Profane, Trask uses  "For" as a coordinating conjunction to begin sentences several times:

Passing over the rational and speculative side of religion, he [Rudolph Otto] concentrated chiefly on its irrational aspect. For Otto had read Luther and had understood what the "living God" meant to a believer. (8)

Whether it is a case of clearing uncultivated ground or of conquering and occupying a territory already inhabited by "other" human beings, ritual taking possession must always repeat the cosmogony. For in the view of archaic societies everything that is not "our world" is not yet a world. (31-32)

The raising of the Cross was equivalent to consecrating the country, hence in some sort to a "new birth." For through Christ "old things are passed away; behold, all things are become new" (II Corinthians, 5, 17). (32)

This example admirably illustrates both the cosmological function of the sacred pole and its soteriological role. For on the one hand the kauwa-auwa reproduces the pole that Numbakula used to cosmicize the world, and on the other the Achilpa believe it to be the means by which they can communicate with the sky realm. (33-34)

As we saw, to settle in a territory, to build a dwelling, demand a vital decision for both the whole community and the individual. For what is involved is undertaking the creation of the world that one has chosen to inhabit. (51)

     This second type of cosmogony is much more complex, and it will only be outlined here. But it was necessary to cite it, for, in the last analysis, it is with such a cosmogony that the countless forms of the building sacrifice are bound up; the latter, in short, is only an imitation, often a symbolic imitation, of the primordial sacrifice that gave birth to the world. For, beginning with a certain stage of culture, the cosmogonic myth explains the Creation through the slaying of a giant (Ymir in Germanic mythology, Purusha in Indian mythology, P'an-ku in China); his organs give birth to the various cosmic regions. (55; KISS, of course, considers the first  "for," in bold, as a subordinate conjunction.)

We have taken our examples from different cultures and periods, in order to present at least the most important mythological constructions and ritual scenarios that are based on the experience of sacred space. For in the course of history, religious man has given differing valorizations to the same fundamental experience. (62)

For religious man, on the contrary, profane temporal duration can be periodically arrested; for certain rituals have the power to interrupt it by periods of a sacred time that is nonhistorical (in the sense that it does not belong to the historical present). (71-72)

     Since the New Year is a reactualization of the cosmogony, it implies starting time over again at its beginning, that is, restoration of the primordial time, the "pure" time, that existed at the moment of Creation. This is why the New Year is the occasion for "puurifications," for the expulsion of sins, of demons, or merely of a scapegoat. For it is not a matter merely of a certain temporal interval coming to its end and the beginning of another (as a modern man, for example, thinks); it is also a matter of abolishing the past year and past time. (77-78)

It can be said of sacred time that it is always the same, that it is "a succession of eternities" (Hubert and Mauss). For, however complex a religious festival may be, it always involves a sacred event that took place ab origine and that is ritually made present. (88)

It could be concluded that this eternal repetition of the paradigmatic acts and gestures revealed by the gods ab origine is opposed to any human progress and paralyzes any creative spontaneity. Certainly, the conclusion is justifiable in part. But only in part. For religious man, even the most primitive, does not refuse progress in principle; he accepts it but at the same time bestows on it a divine origin and dimension. (90)

This is why the myth, which narrates this sacred ontophany, this victorious manifestation of a plenitude of being, becomes the paradigmatic model for all human activities. For it alone reveals the real, the superabundant, the effectual. (97-98)

     This is what happened in India, where the doctrine of cosmic cycles (yugas) was elaborately developed. A complete cycle, a mahãyuga, comprises 12,000 years. It ends with a dissolution, a pralaya, which is repeated more drastically (mahãpralaya, the Great Dissolution) at the end of the thousandth cycle. For the paradigmatic schema "creation - destruction - creation - etc." is reproduced ad infinitum. (107-108)

It was chiefly the religious and philosophical élites who felt despair in the presence of cyclic time repeating itself ad infinitum. For to Indian thought, this eternal return implied eternal return to existence by force of karma, the law of universal causality. (109)

     Christianity arrives, not at a philosophy but at a theology of history. For God's interventions in history, and above all his Incarnation in the historical person of Jesus Christ, have a transhistorical purpose -- the salvation of man. (112)

The transcendental category of height, of the superterrestrial, of the infinite, is revealed to the whole man, to his intelligence and his soul. It is a total awareness on man's part; beholding the sky, he simultaneously discovers the divine incommensurability and his own situation in the cosmos. For the sky, by its own mode of being, reveals transcendence, force, eternity. (119)

Trilling, Lionel:

On the one hand, the belief in the artist's neuroticism allows the philistine to shut his ears to what the artist says. But on the other hand it allows him to listen. For we must not make the common mistake -- the contemporary philistine does want to listen, at the same time that he wants to shut his ears.
(Lionel Trilling, "Art and Neurosis," 159.)

This comes as a surprise. Nothing in Dr. Rosenzweig's theory requires it. For his theory asserts no more than that Henry James, predisposed by temperament and family situation to certain mental and emotional qualities, was in his youth injured in a way which he believed to be sexual; that he unconsciously invited the injury in the wish to identify himself with his father, who himself had been similarly injured -- "castrated": a leg had been amputated -- and under strikingly similar circumstances; this resulted for the younger Henry James in a certain pattern of life and in a preoccupation in his work with certain themes which more or less obscurely symbolize his sexual situation. (Lionel Trilling, "Art and Neurosis," 160-61.)

The reference to the artist's neurosis tells us something about the material on which the artist exercises his powers, and even something about his reasons for bringing his powers into play, but it does not tell us anything about the source of his power, it makes no causal connection between them and the neurosis. And if we look into the matter, we see that there is in fact no causal connection between them. For, still granting that the poet is uniquely neurotic, what is surely not neurotic, what indeed suggests nothing but health, is his power of using his neuroticism.
(Lionel Trilling, "Art and Neurosis," 169.)

I have brought forward Freud's statement of the essential sickness of the psyche only because it stands as the refutation of what is implied by the literary use of the theory of neurosis to account for genius. For if we are all ill, and if, as I have said, neurosis can account for everything, for failure and mediocrity -- "a very serious impoverishment of available mental energy" -- as well as for genius, it cannot uniquely account for genius.
(Lionel Trilling, "Art and Neurosis," 171-72.)

Berlin, Isaiah:

There cannot be mass conversions, for the fate of human groups depends not on free actions -- the movements of the spirit -- in the heads of men, but on objective social conditions, which guarantee the salvation of one class and the destruction of its rival.
(Isaiah Berlin, "Marxism in the Nineteenth Century," 138-39)

The  values of rational creatures must, therefore, according to this line of thought, be enjoined upon me by myself, for if they issue from some outside source, I depend upon that source, and am not free.
(Isaiah Berlin, "The Romantic Revolution," 177)

There are, indeed, many hotels, for the entertainment of tourists is the business of the place, which, as many travelers will remember, is seated upon the edge of a remarkably blue lake--a lake that it behooves every tourist to visit. (The second sentence of Daisy Miller.)

For Trask's use of "For" as a coordinating conjunction, and for the source of the quotations, click here.

Otto characterizes all these experiences as numinous (from the Latin numen, god), for they are induced by the revelation of an aspect of divine power. (9)

This pole represents a cosmic axis, for it is around the sacred pole that territory becomes habitable, hence is transformed into a world. (33)

     That problem is too complex to be discussed here. In any case, it lies outside the field of our investigation, for, in the last analysis, it implies the problem of the opposition between premodern and modern man. (93)