Research (dental-related even better), shadowing a dentist (a gen dentist most importantly, and specialties if you're interested), join your school's pre-dental society, be active in any other clubs/sports, volunteering, something to demonstrate hand skills (take a pottery class maybe?)...It's just about being dedicated to the dental field and showing that you are a well-rounded person (a high GPA doesn't mean much when you don't do anything but study!)...these are just some of the common ones, but of course there are many more!