Register for the PSAT exam in October - the scores count towards the National Achievement Program (and it's good practice for the SAT)
Go to college fairs in your area
Start your college search process. Think about what is important to you in a school. Is location important? Do you have a specific major you wish to study? Start researching colleges that you might wish to attend.
Maintaining your grades in your junior year is important! Colleges put a lot of weight on your achievements during this year.
Make sure you are challenging yourself academically. Colleges consider how difficult your courses are.
If your schedule permits, stay involved in school, community and job opportunities.
Prepare for taking the ACT and/or SAT exams in the spring
Research the requirements of the colleges you are interested in and learn admission deadlines
Talk to teachers and administration about letters of recommendation for you
Consider looking for a summer job or internship
Plan your college visits. Be sure to contact admissions office; talk to professors, sit in on lectures, visit dorms talk to students.
Are you on track to graduate? Are you interested in concurrent enrollment: taking college level courses for high school and college credit? What does your academic record look like? Review it with your counselor and talk about ways to improve? Do you know the admission requirements for colleges you are interested in?