Check out this guide:
http://wiki.project1999.com/Players:Newbie
Basically, what the game is about is killing monsters. Quests, despite the name, are not such a big focus; most of the quests in the game are not worth doing (unless you just want to learn about lore and such). I wouldn't say you can ruin your character per se, although misallocating starting stats can be a little annoying in the long term, and it is possible to ruin your faction with important NPCs (although not so much in the early levels).
Once you hit level 5 or so, check out Blackburrow - newbie dungeon near Qeynos, fairly popular, you should be able to find groups and such. There are also some very nice newbie quests in the Qeynos area (despite what I said earlier), if you are not an evil character: gnoll fangs, rabid bear pelts, broken staff quest, bandit sashes, greater lightstones. Qeynos is actually kind of unusual in that it has a lot of really good quests for characters in the 1-15ish level range.