In addition to what everyone else has said, and I know that this is a year away, find old AP exams to see what the questions are like. If you know that then you can kinda figure out where you need to spend more time. APUSH wasn't that hard, but the AP test was asking for details and specific examples.
When you take notes, take them as science notes. Literally make the social sciences a "science" if that will help you study. Then there's the standard ask classmates for help with studying/notes, ask the teacher for help/advice/transfer (AP is a choice, not a requirement), ask upperclassmen who've taken it for their advice.
Honestly, it wasn't that hard. You'll be about 1.5-2 weeks ahead of the regular US history class in the book, so not that big a deal, and you'll be expected to elaborate more and give better details. In other words, the comparison to writing a story isn't that far off if you're doing some world building or lore crafting.