I have officially been playing since January 07 now, hit the big 1 year.
most of my play has been solo up to this point, with only one RL friend online. He has a lot more time to play than I do, so it's only once a week or so we get on together.
I've solo'd a lot of the career so far, with some running with, normally, one of his higher level guys through instances, or something like that.
Only when I reached Tanaris, did I start actually looking for a group of people to level with. When you're just out questing, you'd be surprised how much the group doesn't care if you don't play a cookie cutter "role". Just help complete the quest, and not too many people are going to complain.
In an instance, there is more of a "role" to play for your class, but I've found as long as you let folks know you are still "finding yourself" they will give you tips on how to better play your class, and won't yell L2P!!!11one if you do cause a wipe.
If you are in a group you don't feel comfortable in, ditch it, find another group. While I haven't done this often, if someone insults me or doesn't like the way i'm doing something, I leave, plain and simple.
I'm a ret paladin on my main, trying to hit level 50 today. I ran SM as the healer the other day, and we wiped horribly, and repeatedly. I did tell teh group before we went in that healing wasn't my thing, but if they could keep the mobs occupied, I could get it done.
They didn't, I couldn't, and again, we had a terrible time, BUT, no one was mad at me because I said before we started that I sucked ;P I still felt bad for the group wiping, but it's not only you playing remember. Our tank wasn't that good, and we had 2 hunter running around trying to use both their pets as tanks... on different mobs than the warrior was fighting... so it wasn't just me by far :)
Happy grouping, get in there and do some stuff... with other people :)