actually what the OP says is fairly common for kids at many state schools, including the top ones. They got good grades in HS without much effort or interest in the material. But they get to college and all of a sudden all the other kids are the ones that were doing well in HS, so the pace can/does step up. I'd echo the advice about 2 hours outside of class for the hour in class; how you spend the time will differ depending on the subject, but I'd say err on the side of caution and start by putting in the time. You can always trim back if its overkill, but one thing that's almost impossible is to catch up when you've fallen behind.
There's a book I recommend to all college students called "What Smart Students Know". It is written by one of the co-founders of the Princeton Review prep service, and explains how to prepare for and study different subjects. Really a great explanation of how to use your time effectively, take notes, etc. This is exactly what the OP has asked for.
Also a web page with links to lots of useful handouts on the subject is at
Helpful Study Skills Links