Hi lsatchallenger,
A lot of it just comes down to practice. Make sure to practice untimed at first so that you can develop each step (such as prephrasing, sorting the answers into contenders/losers, etc.) without worrying about the clock. As you go through each answer, keep your prephrase in mind and notice if any answers are similar to your prephrase. Once you build your skills and confidence, then gradually incorporate timing.
Prephrasing is a skill that improves with practice. It's not just a matter of doing a lot of LR questions, but thoroughly reviewing those questions. After you check the answers, compare the right answer to your prephrase. If your prephrase was different, try to determine whether it would have been possible to prephrase the right answer. It's not always possible, but it often is.
When doing an LR section, also keep in mind where you are in the section. Knowing that earlier questions are usually easier on average can help you to avoid second guessing yourself. Not every question on the LSAT is a trick question; some are actually fairly straightforward.
On a related note, as a general rule, you shouldn't change your answer once you've chosen an answer unless you feel certain that another answer is better and can identify exactly how/why it is better.
We also have a podcast episode (Episode 66) specifically about choosing between two tempting answers that you may find helpful.
It can be found here:
https://www.youtube.com/watch?v=2KwdaRxgMnk