STUDY WITH PENCIL AND PAPER: Solve problems, draw graphs! Be active while you study! It's harder work, but will you'll learn much more in less time.
STUDY WITH OTHERS: Even if you feel your friends aren't very bright, it's still probably useful to study together. They will probably understand some things you don't and vice-versa. Explaining econ to someone else is an excellent way to learn. If you study with someone who is doing too well, you may be encouraged to believe you're better prepared than you are. So, it's okay if your study partner isn't the brightest :-).