I'd ask that dentist or other dentists if you could work for them. You'd probably end up doing a lot of scut work (filing charts, changing over rooms, etc...) but should have a good opportunity to learn a great deal as well as get some practical lab and office experience (pouring up models, processing x-rays, waxing). I'm working as an intern for a dentist right now, and its been a great experience and what I know a heck of a lot more about dentistry now than I did a year ago. Also, maybe look into working/volunteering at a dental lab. Should be a chance to gain some valuable lab skills.
The best thing to do is watch. I was offered a job about six years ago while I was in high school and I have been working at that office ever since when I have a chance. I've been trained to do every job in the office by being interested in learning about my future profession. That job lead into another one with a group OMS practice where I learned to do everything there too. I am able to assist on any procedure and know what instruments are needed for what procedure and how to use them - that will be helpful I'm sure when I start dental school in the fall.
I have made a lot of great connections for my future. All it takes is enthusiasm and you can get whatever you want.