Review the Kaplan book (forwards and backwards), and you'll be pretty much good to go. Take the practice exams in the book, and throw in the TopScore exams also -- but take these in the last 7-10 days leading up to your exam. Use the questions you missed on these exams to help you do last-minute studying.
Then take the test!
The bad thing about the DAT is you can always push the test date back. This rarely helps (unless you really have NOT been studying anything). I believe a person can do very well on the DAT with only two weeks of studying. Of course, that would be 2 weeks of studying 8-9 hours every day.
I set a study pattern for myself, which was something like 5-6 hours every day for a month. It worked out fine. Study hard and then get the test over with.
Good luck.