PK - AK has said it best - "work your *** off". You study, do the assignments, turn in the assignments, be in class, prepare for tests, work hard on projects, ask questions and for tutoring if you don't understand, and do any extra credit that is offered". You just simply have to care about your grades! Waiting until your senior year is too late.
AK is a wonderful example of putting his nose to the grindstone and what it can do for you!