Academic Choices in HS Affect College Admission
Many times, high school students do not realize the importance of taking a challenging curriculum in high school, but also performing well within those classes. By the time you enter 11th grade, you have already established half of your gpa/rank that you use to apply to colleges your senior year.
Another issue would be to be involved in extra-curricular clubs and organizations as well as volunteering for community service opportunities. It's important to show leadership and in-depth involvement.
It's also important to take a challenging schedule every year. Be careful not to over-extend yourself academically as it can have a reverse affect on your gpa. In that case, focus on taking your rigorous classes within your strength subject areas.