My understanding is that now you sign up and are given a date within a certain amount of time from when you sign up to take the test. The test is given the first three weeks of every month. You can only take it once per month though, so if you plan on taking it more than once you need to sign up with plenty of time for leeway before your applicaiton deadlines.
The sittings are individual, not in huge groups like we are accustomed to with standardized tests. Amycat, my best friend took the GRE a couple of years ago in Santa Monica at a testing center. It was so cool, she took the exam on computer and they gave her the score. Nothing like the 6 weeks I had to wait for the LSAT.
Another good site is
www.kaplan.com. It walks you through how to schedule your exam date and all the ins and outs of applying to grad school. According to the site you can download the registration materials from
www.gre.org.
Take care.
Laura