I started studying two months prior to the date I had signed up for the LSAT. I found that two months was just not enough time to get closer to the score that I was aiming for. So, I postponed and took another two months to study.
I know one person who only studied for one month and ended up with a score in the mid-170's. She is a genius and an exception, in my opinion.
My advice is to give yourself plenty of time to prepare, at least six months. For example, if you are signing up for the June 2006 test, and you start now, you will have about 4-1/2 months to prepare. However, if you feel as you get closer to the date that you need more time, then postpone to October 2006.
The main thing is to get the basics down. The books that are mostly recommended are the Powerscore Bibles, there is one for Logical Reasoning (approx 50-52 questions out of 100-101 questions) and one for the Analytical Reasoning (games).
Most people cannot digest that much material in a short time. Some people prepare in two months, but it is a challenge to learn how to approach the different sections and to learn the test and
to get good at it when you are taking the sections under timed conditions.
Hope this helps.