If you haven't signed up yet for the LSAT, the deadline is next Tuesday.  All the testing sites in the area still have plenty of room. If you don't sign up by Tuesday, it will cost you an additional $69 to sign up through the 14th.  After that, you can't take it in October.  September 14 is still 3 weeks away from the day of the test so if you are waiting until you feel ready to sign up for the test, you may have to just sign up for it.  There is a lot of learning that can go on between now and then and it is hard to judge that far out if you will be peaking by then.  The good news is that if you get to the end of September and realize that there are some concepts that with a bit more work, you will get them, you can sign up for the December test and just not show up for the October one.  The only consequence is that you are out the $160 that it cost to sign up to take the test.  The law schools do see that you were signed up for the test but did not take it.  However, it does not matter at all in the admissions process.  The law schools want you to take the test when you know you are going to perform at your ability.