Good students: How do you go about getting good grades? [Serious]

Please provide us with tips that everyone can benefit from. Got a certain strategy? Know something other students don't really know? Study habits? Hacks?

Update: Wow! This thread is turning into a monster. I have to work today but I do plan on getting back to all of you. Thanks again!

Update 2: I am going to order Salticido a pizza this weekend for his great post. Please contribute more and help the people of Reddit get straight As! (And Salticido a pizza).

Update 3: Private message has been sent to Salticido inquiring what kind of pizza he wants and from where.