Most of what's on the A+ test is stuff that you've probably picked up on your own. What you need to find out is what obscure stuff will be on the test. There's no "trick" questions but there are a handful of items related to things that you might encounter once in a blue moon.

I don't think the practice tests are worth the money (I looked at a couple after I passed my certs). Just get a couple of different test prep books and don't focus on what you already know.