From what Ive experienced, most advisors really dont have the best advice haha.
Key to getting a 19+ :
-Bio:
Cliffs AP Bio (10$) + DatQVault (22$ for 500+ questions) + Alan's Notes (free) + Campbell (you should have from Bio courses, for Ear/Eye/Histology/Brain/Ecology) + Seeing as many multiple choice questions possible (Campbell's online quizzes that come with the book are amazing)
-Chemistry:
Chad's Videos (30$) + DAT Destroyer (200$ w/ Math Destroyer) + Alan's Notes (free) + 2-3 Practice tests (60-80$)
-Organic Chemistry:
Chad's Videos + DAT Destroyer (especially the roadmaps) + 2-3 Practice tests
-Perceptual Ability:
Crack DAT PAT (10 test addition to get your timing down) is all you need
-Reading Comprehension:
Crack DAT Reading (remember to practice this, much more influential on getting in than you'd assume)
-Quantitative Reasoning:
Math Destroyer - this is a must (usually people tend to neglect this section, thus dropping their AA a point or two, practice this early on studying by timing yourself 40 questions in 45 minutes. the section is, personally, the most difficult due it being at the end of a 4.5 hour test AND that it's pretty tricky.)
-Practice Tests:
Topscore seems to be the best practice test material, along with the ADA 2009 test.
Good luck! Plan ahead and make sure you order a decent portion of these materials before you begin to study. Helps a lot to have it all when you need it and not rely on the mail(wo)man.