Thanks for the question, and welcome to the Forum!
This is a common one, where people often wonder about the "dangers" of selecting an answer and moving on without giving the remaining options any thought. In fact, we've addressed it quite a few times before in this very Forum:
http://forum.powerscore.com/lsat/viewto ... f=2&t=6772
http://forum.powerscore.com/lsat/viewto ... =15&t=1607
http://forum.powerscore.com/lsat/viewto ... f=2&t=4462
http://forum.powerscore.com/lsat/viewto ... f=2&t=6287
http://forum.powerscore.com/lsat/viewto ... f=6&t=6439
And that's far from an exhaustive list. Point being, test takers ask about this a lot.
My personal take is that you should always strive to read every answer in LR and RC (LG less so, as right answers there tend to be more easily/definitively proven), since the test makers are notoriously great at making wrong answers appear attractive, and disguising right answers so that they're not initially appealing. But I realize that time considerations play a role and reading 125 answers (roughly) in an LR section can be a tall order.
With that in mind, let me remind you that it's all a matter of measurable quantity: do you regularly come away with more points by finishing 20 questions on a pick-the-first-answer approach, or by finishing 16 questions and reading every answer? Seems easy enough to determine with just an A/B comparison. So time yourself with both approaches and see!
Ideally speaking you read everything...realistically speaking though some adjustments may prove necessary, and that's okay! The key is capitalizing on the measurable nature of both, experimenting a bit—even in terms of confidence; maybe only select and move for answers where you're extremely (80+%) certain they're correct—and using those results to dictate what's most appropriate for test day.
Keep me posted on your progress, and let me know if you have any additional questions!
Jon Denning
PowerScore Test Preparation
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https://twitter.com/jonmdenning
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http://blog.powerscore.com/lsat/author/jon-denning