Most of the pedagogical questions related to English usage are not among my major interests. I have enough headaches from wrestling with the questions of how to teach sentence structure. The two areas do, however, overlap and questions of what to do about usage problems sometimes arise. For anyone who is interested, I compare syntax to the human skeleton; usage, to our clothing. We are, for better or worse, judged for both. To a large extent, I agree with the opinions of David Foster Wallace (See below.)

Garner, Bryan A. A Dictionary of Modern American Usage. Oxford University Press. 1998. 723 pp.

Gilman, E. W. ed. Webster's Dictionary of English Usage. Merriam-Webster Inc., 1989. 978 pp.

Gove, Philip, ed., Webster's Third New International Dictionary of the English Language. G. & C. Merriam Company, 1961. 2,662 pp.

Partridge, Etric. Usage and Abusage: A Guide to Good English. Hamish Hamilton, 1957. 392 pp.

Wallace, David Foster. "Tense Present: Democracy, English and the Wars over Usage." Harper's Magazine. April 2001. 39-58 [HX]

      When Brock Haussamen brought this essay to the attention of the members of the ATEG list, I went to the library and got a copy, mainly out of a sense of duty. When I found that it is twenty pages of small print, I told myself I was never going to read it. I expected, especially from the first page, a holier-than-thou, snooty condemnation of those of us who are not particularly concerned with the nicities of "proper English."  Wallace himself notes that he is a "snoot," but he is, in addition to being witty and self-deprecating,  a very level-headed snoot. After two hours and five minutes of reading (I log my time.), I wished that the essay was longer. 
     On its surface, this essay is a review of Bryan A Garner's. A Dictionary of Modern American Usage. Wallace uses the review, however, not only to give an excellent background on the "Wars over Usage," but also to make some very sensible suggestions about what the average educated person's position ought to be relative to these wars. He shows the flaws in the extremists in  both camps -- Prescriptivist and Descriptivist. (In effect, he argues for the Aristotelian middle position. Perhaps that is why I like him.)
     The article is well worth the two hours it may take to read it, and I highly recommend it for people who turn to books of usage for "authority," especially for those who have only one book. Among other things, Wallace shows that the "authorities" are not all in agreement.