Lorithian, welcome to the ESO-world mate! You get to squirm and scratch like coke addicts like the rest of us until launch!
But seriously, choosing which class to play is a tough task. Basically because while each has it's own special feelings to them, they're all VERY much alike. You can very easily build up 2 characters of 2 different classes, and end up with each being almost the same. But it IS those little things, like specific class skills, that give them their uniqueness.
As for which one to pick, for your first character I'd say just think about how you MIGHT want to play and choose the class that SEEMS close. I emphasize those words because it is very easy to start out thinking you're going to be a sneaky thief, and then part way in completely change your mind and become a heavy armor and 2-H Axe user or something similar.
My point is, there are a TON of tools available now with information of each class, each race, and ways to build characters. However until you get to really playing, it's very difficult to know what best fits you.
Still, we can certainly try and help you narrow it down a little!
This could be a decent Bow-Healer for group play. It's got enough bang to get it done, and some nice heals.
For solo play, though similar to the last build,
this build adds in a little more pew-pew 
Basically, think about what race you want to play, do alot of reading on articles and such, and keep asking questions!