Here are some tips when applying to colleges:
Keep track of deadlines.
Ensure you've taken on rigorous courses (i.e. Honors; AP; IB; Dual Enrollment).
Request recommendation letters in advance from teachers and/or guidance counselors who have witnessed your growth or challenges you've overcome.
Write a personal essay that reflects who you are.
Involvement in extracurricular activities/volunteer opportunities within your school and in the community.
Request copies of your high school transcript.
Submit your SAT/ACT scores.
Make sure you visit the campuses of the colleges you are applying to.