make sure you know some of the big books and authors--my AP teacher gave us a list of the 50-most important ones a day before the AP test--I studied it, and BEHOILD, the AP EXAM had 5-6 question on it...
My teacher was banking on last year's dbq on being on vietman, it was on some bull***** agricultural/guilded age/populism...so i guess STUDY VIETNAM, the dbq hasn't been on vietnam in forever so...
I got a 5, but I think my multiple choice score (probably got 72-74 correct out of 80...NO JOKE) helped more than the essays...