Now what?
Alright, you're exploring the world, doing quests, killing things, leveling up. So what else is there to do? Plenty, actually. You could try your hand at PvP or Roleplay, collect Achievements, work on Reputation, etc. So lets break these things down and see how each one works.
PvP - This is not for everyone. Actually, I hate PvP, but some people enjoy it. I covered PvP flags at the start of the guide. You can engage in PvP whenever you like really. You can fight other players out in the world, or join battlegrounds. A battleground is like a large outdoor instance focused entirely on PvP. You can gain experience, loot, and various rewards for PvP.
If you're like me and would rather avoid PvP there are some things you should know to prevent yourself from getting caught in it. Attacking a member of the opposite faction will flag you. If you're a healer and you heal someone of your own faction while they're flagged, it will flag you. Entering into an enemy capital city will flag you. If a higher level enemy NPC attacks you, it will flag you.
Roleplay - Pretty self explanatory, I think... although there are people that have no idea what RP is. You're basically taking on the role of your character and acting things out as they would in the game world. You can even download game mods to give your character a profile in game with a backstory that will let other people see that you're a roleplayer.
Achievements - Doing just about anything in the game will give you achievements. These are little unlockable rewards that can be viewed in your character window. There are achievements for exploring the world, doing quests, collecting mounts and pets, raising reputation, doing instances, PvP, etc.
Reputation - Every time you do a quest for a race or a faction, you gain rep with them. The more you do for them, the higher your rep will be. Having a very high rep means having access to special items from them and getting discounts at shops.