I found the Kaplan course very helpful. I took the DAT 5 years ago.
The classroom helped me stay on track and learn incrementally over the summer. Then, about 4 weeks before my test date, I started studying hard. I think what I found the most helpful were the practice tests and explanations to the answers. I read through all the explanations, even the ones I got correct.
I also used class notes when there were areas that I could identify that I was weak in. For RC, I feel you need practice and a strategy: and tests are the only way to do this.
Furthermore, the DAT is a longggg test... You need to train yourself to sit through that many hours and focus. So I did many "simulation tests" 1-2 weeks out. Waking up at the same time I normally would, traveling to the Kaplan testing center, and taking the same breaks etc.
Since everyone else has their DAT scores: mine was 24 AA 26 TS, 21 or 22 PAT and 24 or 25 RC. I got a great scholarship at my dental school, that I can attribute in large part to my DAT score... The $1000 I paid, pales in comparison to the $120k scholarship.