I don't think you need me to repeat the standard advice: un-tag yourself from photos you don't want colleges to see, make sure you have your school-friendly photos and résumé-building awards on public settings for the world to see, avoid anything that hints at academic imperfection.
The problem with this sort of advice, practical and accurate as it is, is that the overall message and tone of the advice is to consider yourself always watched and always performing. Never say or do anything that colleges don't like, as if all colleges "like" the same things. I advise against doing anything, no matter how productive or good on the surface, simply because colleges want to see you do it.