1) Visit Colleges
Winter Break means quiet campuses with plenty of space to roam. While it is best to tour when the students are around, it doesn't hurt to get an idea as to the general layout of a campus any chance you get.
Use some of your time to give back to those in need. Find an organization you are interested in and start building experience.
3) Develop Your Skills
Take a class at your community center, build your photography portfolio or knit that scarf you've always started but never completed. You will build your skills and hopefully develop some talents that will come in handy later-on.
4) Apply For a Job
Work experience can help an applicant. Polish up your resume and hit the pavement while you have some time on your hands.
5) Work on Your Essays
Are you a junior? Start drafting some essays as practice makes perfect and application season is just around the corner.