Study harder. I'm glad that you plan to further your education. You should spend at least 6 hours a day studying. Of course HS is different. You cannot expect to get an A simply on attending class and doing the required work. You don't deserve a good grade unless you give it your best effort (I suggest 1 - 2 hours per night per class).
Have your goals in mind. Do not do anything that does not advance you toward your goal (eg. getting drunk and passing out) .