I got a 22 in Ochem based off of studying Kaplan. I read through the book and made notes and tried to understand all the reactions. Then I read through the book again and made sure to check my notes that everything was complete. Then I made a huge list of all the reactions (sorted by functionality) and memorized it all. I used the blue book as well as the online resources. The only other thing I used was two of the TopScore science sections. Oh, and I sucked at OChem when I took it in undergrad. C- the first semester, C the second semester, and B- when I retook the first semester. So whether or not you did well in ochem in school, you can definitely own it for the DAT.