By the time we enter College as undergraduates, most of us have a pretty good idea of what we want or hope to become. This idea is what leads to us choosing a particular field of study.
If you wish to become a dentist, you have to first attend undergraduate school and then dental school. Your undergraduate career should be geared towards aspects thereof and you should also engage in activities which will complement your career choice. Some of these activities may include shadowing a dentist or a doctor at his or her own practice, volunteering at your local health clinic or anything related. Note that dental schools like to see well rounded individuals both academically and otherwise. Note also that dental schools have no preference when it comes to your major or course of study. You can usually take any course you wish as long as the prerequisites are fulfilled. Needless to say, you will need to do well academically.