Once you are fairly comfortable with finding subjects and verbs, you should start to look at the full S/V/C pattern. The "C" stands for "complement." To find the subject of a verb, ask a question with "Who" or "What" before the verb. For example, in the sentence
To find the complement of a verb, simply create a question with "whom" or "what" after the verb. "Arthur likes what?" The answer to that question in this sentence is "sandwiches," so "sandwiches" is the complement of "likes."
Note that the question has to be based on the verb plus "whom" or "what." Words that answer the questions "When?" "Why?" "How?" etc. do not reveal complements, they reveal adverbs.
Note: In Level Two, you are expected to be able to identify single words that function as complements, but some complements consist of several words and may confuse you. You will not be expected to identify these complements. Simply concentrate on the complements that you can identify.