Combine this with step 4 and you'll be very well prepared. You simply can't study non-stop, it's not healthy. There are things that are important in life other than school. If you stay physically fit and remember to share a few laughs with your friends you'll feel great and also do better in school. Karen says that after a scheduled study break, she always comes back more focused.
Smarts is a way of thinking and can usually be improved with brain training.
Set reasonable goals. You are not going to rise from 2.0 to 4.0 overnight. Shoot instead for a 0.5 - 1.0 GPA improvement over the course of the school year. Ask yourself if your goal is reasonable. Ask a friend if it's reasonable, then ask a teacher if it's reasonable.