If you don't want to committ just yet, get one of the ITBS test prep books. THey are $7 and have sample test at the end. I found the questions a bit odd so I was glad I splurged for a book so that DS learns how to fill in the bubbles.
For ex: on Capitalization and Punctuation section a question reads:
5A After we watched the fireworks
B from Uncle Vic's front window
C monica and I went for a walk.
D (no mistakes)
So one sentence runs across all 3 answer choices rather than individual sentences for A,B, and C.
