The questions on the test are about at the $32K level. There were quite a few science questions when I took it, running the gamut-- biology, astronomy, chemistry, etc. The others were all over the map. I didn't study for the test, and for the show I only crammed on maps (figuring that visual information was the most likely thing to stick in my brain at the last minute-- and it would have worked for me if I'd been a couple of contestants sooner, when a question came up that I only knew because of my map cramming!).
The biggest piece of advice I can give you isn't about the test, which you'll either pass or you won't-- I really don't think there's much you can do to prepare yourself in advance for it. The interview and application are an entirely different story.
The smartest thing I did that day-- apart from showing up early enough to be admitted-- was that when they handed me the application form after I passed the test, I didn't rush through it. In my group, about 20 people passed the test. They did 3 audition groups that day. That's about 60 people passing the test. I knew all 60 wouldn't make it to the show. In fact, I couldn't imagine more than 5-10 would. So I had to make myself stand out and present myself as someone who'd make a good contestant and good television.
They give you about 10 questions and ask you to answer half of them. Stuff like:
* What would you do if you won $1,000,000?
* You'd never know it, but I...
* Tell us about your hobbies
* My most embarassing moment was...
* I'm most passionate about...
and so forth. If you get this far, really think about your answers. Find ways to respond that will set you apart from everyone else. Think about what's unique about your life and experiences. What would make for a good story for Meredith to talk to you about in the hotseat? That application is the real audition. Treat it that way.
After filling out the application, you'll talk very briefly to a producer. Be positive and upbeat, but natural. Be coherent. Demonstrate that you can speak clearly and think on your feet. Show them you won't be a lox on camera. Hopefully, this just means to be yourself. I suspect it doesn't matter how many questions you get right on the test-- if your application doesn't stick out and you're a zero in the interview, you'll never get into the hotseat.
Good luck!