They'll send a short sample booklet a couple weeks before EXPLORE, but there is a full length practice test available on the ACT website for about $5.
As far as prep, I had my oldest DS go through the guide/sample test that came with registration for both ACT and SAT. We read the rules very carefully and reviewed the answers. I did the same with second DS but his interest petered out. He was weak in math, so we did some practice from an ancient SAT math book I had (I think this only served to intimidate him because there were so many he didn't know how to work). It's impossible to teach them at this point, so the important thing is that if you narrow a question down to 2 answers, take the guess; otherwise leave it blank. The best thing is to go over that kind of "strategy" with your child, rather than covering more material than the practice test.
For DS 11, I did have to reassure him that this was supposed to be a fun challenge, that the results don't matter at all at this point, so try not to stress, that no one had to know if he bombed it, that it was good practice/experience for when it did matter (when applying to colleges), etc. I told him not to exhaust his energy on the essay because it didn't mean anything for the talent searches and he didn't have enough life experience and essay writing to do well, so save his strength for the other sections. DS 11 was not having it--he loves writing and said that was how intended to get "worked up" for the rest of the test. We'll see where that put us...
