Study, get a tutor, ask for extra credit, put 110% into every assignment, including actually doing every assignment, not just when you feel like it, take a lot of notes, make flash cards for new information, don't save things for the last minute
Do your homework and take your time on it. Try to get into a pullout class for the subjects you need work o. Go to bed early and make sure you HAVE A LOT OF REST!! If you have any questions in school, ask. My teachers are prob annoyed of me for asking so many questions, but i helped me understand, Good luck!! :)
Do your homework and turn it in on time, study for tests and quizzes, pay attention in class, take good notes, and try to get enough sleep, 8-9 hours works amazing, even better 10 hours! You may find it crazy, but you feel so much less drag in the morning! Also, eat breakfast (I don't usually, I just drink coffee normally) but yeah, that should just about do it.