CLAT

From your question, it sounds like you're interested in classroom coaching centers. If that's the case, I'd suggest doing your homework thoroughly - there are quite a few institutes that charge hefty fees without providing anything in the name of quality. Here are some basic tips to keep in mind:
Quality of the faculty - many places hire recent Law grads who couldn't land a job or pretty much anyone else who can teach. Check that you are being taught by someone who actually knows what they're talking about and are qualified to teach
Results of the institute - however this is hard to verify because all coaching classes claim the same few students as their own, when in reality the student may have once visited the branch for a mock test or something
Your commute - if you're going to be visiting the same place for several months, it better be convenient for you otherwise you're going to be wasting a lot of time commuting.