Seek paraphrases, not guesses
Oftentimes the correct choice to these questions is simply a paraphrase of the concluding sentence. So, if you are able to separate the premises from the conclusion, then the correct choice will be fairly easy to spot. See (E) for LSAT PrepTest 50, Section 2, Question 4. Also see (E) on LSAT PrepTest 50, Section 4, Question 25.
Don't guess what the author might be leading up to. Do not attribute a conclusion to an author that s/he does not make. For example, LSAT PrepTest 50, Section 2, Question 20. The author concludes that many environmentalists' worry is unfounded. But, the author does not take an extra step and then claim that any action should be taken. Choices (A) and (E) provide guesses as to what the author might be leading up to.
Separate premises from the conclusion
A common incorrect choice will list a premise, rather than the conclusion. The choice is tempting because it repeats passage information, but, does not answer the question. See LSAT PrepTest 50, Section 2, Question 20. Also recognize secondary conclusions and separate those from the main conclusion. See (C) and (D) on LSAT PrepTest 50, Section 4, Question 25.
Recognize examples
Sometimes a passage will contain an example, which is definitely not the author's main point. See the second sentence on LSAT PrepTest 50, Section 1, Question 4, and then see (D).