They're annoying and hurt a little bit at first, mostly just gave me a headache.  You get used to them being there eventually though.. They have these little brushes that help you clean your teeth under the wires, its sort of like a toothpick but has a brush on the end.. so be sure to ask if they have some.  Keep your teeth brushed, told its a lot easier to get cavities with braces..  Um, eat soft foods when ya first get them, like mashed potatoes.. once you get used to them it won't bother you to eat other stuff.

I've had braces for 1 1/2 years now, my sister had hers on for a year...so unfair   but they aren't that bad. Hurt for a while, first time I could only eat mash potato

It depends on what you're putting.
My sister had to widen her upper jaw so she had a little box on the upper part of her mouth and every night she had to use a little key to spread the wires that came from the box to push her teeth out. She had a V jaw and had to turn into a large U because of her teeth. That, according to her, HURTS a lot. Well, you are forcing your bones to extend so... Normal.
Later she just used a normal kind of braces on the upper teeth to put them in place and she said it was just uncomfortable because she couldnt eat everything and at night, if she didnt use the wax, it would injure her.
A friend of mine had hers for less than a year on the upper and lower part to straighten her teeth and it was troublesome because she had rubber bands attaching both parts and they would force her to almost keep her mouth shut because they were strong. Again, also the wax thing and be careful because some parts of the braces might pop out and stick out and cut your mouth. I think it's called brackets, the parts that jump out easily....
But after 2 months or less, you get used. As they said, keep it clean! Braces are always something that call attention and if you have dirty braces, it's horrible...
I never really had braces because I was lucky enough to have straight teeth.. But at 14 I fell and got 4 teeth on the front slightly to the back so there's a little shadow when I smile but nothing much.. Though, I have a friend that is still using her braces and she started when she was about 5 years old. She's almost 20 now. She had her teeth really badly placed so even when she was a kid, she needed to put them straight and then they would fall and come again and she would always be changing braces.

Ah in the end, you'll use this... Plastic thingy that is the molde of your teeth as soon as you take the braces which is how they are supposed to be and you will have to use it during the night so that your teeth wont return to the damaged form : D It might hurt a bit since during the day, they move slightly and it will take a couple of months until it all gets "secured".
Remember to ask your dental doctor what you'll be really doing: if you need to extend your jaw or just put them in place so that you'll know which situation you'll be in and if you'll have to use upper and bottom or just one of those.

Good luck!

WOW thanks a lot guys for all these infos that was amazing, thanks again. I gotta say I'm a bit scared.