High school is seriously just the time to buckle down and study, while balancing clubs, more serious volunteering, and maybe work. Grades seriously do help w/ getting into schools and getting good financial aid, and all I really know about studying is that working hard is a habit and it takes anywhere from 18 days to 254 days to form a habit. When studying for a test, you may be tempted to tap open a Chinese novel to motivate yourself, but unless your self-control is better than mine, that one glance is the road to an all nighter caused by procrastination.
For people in their junior and senior years (in the US) who want to go to colleges out of state, you may want to look into Posse and Questbridge scholarships.