Perhaps the biggest difference between high school and college is that in college, you are expected to get A LOT of your information and learning from reading. In many cases, that will mean reading a text book, though it could also be reading material posted on a website. In either case, you must be an ACTIVE READER - that means you must be thinking about what the author is trying to tell you. You have to keep asking yourself if you understand what he or she is saying. How often should you ask? Every paragrah!
The whole purpose of the paragraph in non-fiction writing is to separate one idea from the next. If you miss an idea, the next idea probably won't make sense (nor will any of the ideas that come after). You're going to have to read A LOT in an AP class and in college so you don't have time to read things 2, 3 or 4 times over. You want to read it, get the main idea and then work on remembering that main idea as well as any other key points in the paragraph. (Key points are those which support the main idea. There can be information in a paragraph that does not support a main idea, and therefore you probably don't need to remember it.) For work spcecifically on finding main ideas go to the Finding Main ideas page by clicking the brown words in this sentence.
How can you remember the important stuff? Going over it several times is great, but there's a limit to how much time you have in your day to do this. (And over the course of a semester or year, that could get to be a LARGE amount of information.) Another way to remember things that doesn't take long and really helps is to write it down. Writing will help you remember! Also, use as much color as possible and have those colors mean something such as "Main idea" or "Key detail" or "Word I don't know the meaning of."
Finally, your vocabluary is never going to get any bigger and you'll never become a more accomplished (and quicker) reader if you don't learn new words. By reading books that give you new vocabulary, you'll expand your vocabulary but only if you NOTICE the words you don't know and then FIND OUT what those words mean. Many students skip one of these steps and therefore don't improve their vocabularies.
Below are the first few pages that a student in AP World History is expected to read. This is what your reading should look like when you're done. If you can't write on what you're reading (such as this packet or your text book if you don't want to have to buy it) you should take notes on a separate piece of paper. It will take a bit longer than highlighting, but is actually a better way for your brain to remember what you've read. The extra colored circles and text below represent the following:
Main ideas are in blue
Words you don't know (I'll bet) are in green
Active reading notes are in red
The passage below is from Guns, Germs and Steel: the Fates of Human Societies (1999) by Jared M. Diamond