In reply to Sharp: definately find one that you like. Theres always the vicious cycle that affects some people, and unfortunately its usually the ones who dont look after their teeth. Dont go cos scared, have pain, go, have to have difficult extraction / filling, scared, dont go, etc etc.
Ive seen a few people who never need any fillings or cleaning work done, it is possible, myself for one example, Im human too!
It can help to find a dentist who explains whats going on, that can be reassuring. You could have some treatment done whilst sat up, some people find lying down makes them more veunerable, but having said that there are some treatments that a dentist cannot do whilst you are sat up as its impossible to see and very bad for their back/neck.
Go and have an examination, have some simple dentistry done first, cleaning and polishing, temporary fillings etc whatever they can offer to get you used to having things done in your mouth.
Some places may be able to offer you to watch whats going on, either with a large mirror or with a video (very fancy stuff), and that might help you.
I find that when Im seeing kids or anxious people, so long as they are willing to leave their previous experiences to one side and not hang on to irrational thoughts and worries, that as I go along and explain what Im doing and what to expect next, they are ok and can relax.
The ones that I cant help are the ones who arent willing to help themselves and insist that everything is going to be awful and painful, they often dont hear what Im saying and just sit there petrified for no reason, other than their own imagination.