Decide your play style - the glory of open-ended RPG
Heres an example of the things you can do if you get bored with grinding:
Develop your profession - get skill points or make some money.
Browse the Auction House for good deals or epic lewtz.
BATTLEGROUNDS!
Start a new character (try diff race/class)
Respec! This is fun because each talent spec dramatically changes gameplay and combat.
World PvP, raiding, getting onto a roof in a small enemy town and killing lowbies.
Duel someone.
Buy a fun outfit and run around a main city.
Go help your friends quest or run a friend through an instance.
Hang out in a main city and chat or interact with other characters.
Befriend an enemy character.
Join a guild or start a guild.
Dance with, slap, or kiss other players.
Hit on a Blood Elf babe.
Go fishing.
The game doesn't have to be boring unless you make it that way by grinding alone for 3 weeks straight.
Be sure to pay attention to your TALENTS, the AUCTION HOUSE, and BATTLEGROUNDS. And most importantly make it a point to INTERACT WITH OTHER HUMAN BEINGS WHILE PLAYING! Especially if they're RL friends!