i took it a few years ago - and it's easier than the lsats...
get one of the test prep books and if you're a weak test taker (how'd you do ont he sat's) and the gmat's are really important -take one of hte kaplan courses - they give you all sorts of "tricks" and techniques to score higher
they're difficult tests to study for -because it's based on basic skills
if 550 is the minimum - I'd shoot higher than that - and how was your GPA out of what type of school? some schools put more weight on GPA and school -than on the GMATs...