The easiest way to see the field of dentistry is to ask a local dentist to shadow at the dental office. However, this is just more observation rather than doing. This will at least let you see the procedures that dentists do because being a patient is a whole different perspective.
Free dental clinics allow you more hands-on experience with chairside assisting. However, some Free Dental Clinics may have quite a process to start volunteering at the clinic-- paperwork, TB shots, tetanus, etc (check with the dental clinic you want to volunteer at). It also depends on where you currently live right now, which state, and city.
Some other people choose to apply for programs that allow you to go to some sites nearby to do community work with some dentists. However, this usually requires some travel and money.
Definitely suggest that you print a bunch of copies of your resume and visit the clinics in person. Shows your dedication, and plus, more likely than not, the receptionist will take your call and never return it.
Are general dentists preferred or should I also try calling specialists? Also, would you ask the secretary on the phone or ask the dentist to get back to you?