There are a lot of ideas on how best to prepare for the LSATs, including spending hundreds of dollars on prep classes by groups such as Kaplan. I'm pretty good at taking standardized tests and, furthermore, I didn't want to spend $500+ on the type of preparation that doesn't usually work for me. Instead, I went to the LSAC's website and ordered their actual past LSAT tests and practiced on those for several weeks before the December administration of the test.
If you're going to take the LSAT, my advice is simply to take actual former LSATs. Skip everything else, especially practice LSATs that were simply made up and aren't authentic. Time yourself, but give yourself a little less time than you will actually get (I used 30 minutes when I knew I'd actually have 35). For each section I recorded how much time it took me and how many of the questions I got right, plus when it was taken. This taught me that it was very important to my abilities to take the test after a good night's rest, to eat right, and to stay in practice, as my scores after staying up late, eating a lot of junk food, or not practicing for a few days were always lower. It also gave me a realistic understanding of what I'd get, as my scores consistently were between 160 and 169 (not absolutely amazing but still very good). The Logical Reasoning and Reading Comprehension sections were easy for me, but remember to read the questions carefully. From timing my sections I came to realize that I would have plenty of time to read each question carefully, and doing so helped bump up my score by a handful of points. It was the Analytical Reasoning ("logic games") section which gave me trouble.
For the Analytical Reasoning section, I didn't even finish it within the time limit for the first several practice tests I took. There were two main reasons for this. The first was that I was trying to diagram out every part of the question, rather than simply trying to find the answer to what was being asked. The second was that I wasn't recognizing patterns. The AR section tends to have four sets of questions, with six or seven per set. The first question in each set can usually be figured out without even creating a rudimentary diagram, as four of the five options can be eliminated directly (for instance, knowing that "Amy" can't be the answer for who is present on Wednesday because you are given the condition "Amy must only work on Monday"). In case you missed it, the names are usually one per letter, such as Amy, Betty, Carol, Denise, Emily, and so on, which means that you can simply identify them by letter when you diagram (each second is valuable). Remember that the questions in each set get harder and that each set is harder than the one before it. Don't spend too long on each question; if you can eliminate two answers but are stuck, guess. There's no penalty. You may also want to bring an analog watch (no danger of beeping) with you to the test. At about a minute or even just thirty seconds before the end of the section, guess on any questions you haven't already answered. If you've got five left the odds are you'll guess at least one right, and that could be a whole point on your final score. Again, there's no penalty, so even getting them all wrong doesn't hurt you.
It's very important to keep your mind in shape. Take at least one practice test a day in the weeks before the test, and take two if possible. You want to do the entire test in one sitting and you want to shut out all distractions such as TV or your phone (although taking one or two with distractions may be helpful to help you learn how to shut out noises like someone with a sniffly nose, the person who taps their pencil as they think, or a creaky air conditioner).
If you prepare then there's no reason not to be confident when you go in, so long as you're realistic. I knew I'd prepared and that I'd done well on standardized tests in the past, and so I was relaxed. I'd already printed out my LSAT admission ticket and laid out my clothes for that day the night before and I had three mechanical #2 pencils. I didn't expect to get a 180, but I also knew that even if my mind completely went blank I would probably get at least a 155 (my lowest practice score was a 157 taken under terrible conditions). Don't concentrate on wanting a certain score so as to get into a specific score; do your best and take it from there.