Become one.
Just kidding, there are several things you can do.
1. Become a dental assistant, although this doesn't seem to have too much importance (as far as I can tell) as you may think for admissions.
2. Volunteer at dental outreach programs that provide services for free to those who cannot afford to pay. Contact some local dentists in your area to see if there are any you may be interested in.
3. Join your school's predent society, they can usually do a lot for helping students get acquainted with the field.
4. Go on a mission trip to other countries. Several of my friends did this, and it seemed like they learned a tremendous amount as well as got to do dental work on patients! This is due to the complete lack of care in some poorer areas, they will take anything they can get in some places.
Hope this helps. Jay