Most of us probably have alts at this point. On my main server, I have a character of each class (and besides the shaman and the mage, they're all at least level 40). And all of them that have leveled past Feralas have a Sprite Darter Hatchling to love and call their own. I like keeping at least something constant across all the different classes.
I've met people who use consistent naming schemes, which is helpful because it makes it easier to tell which alts go with which mains. I've met people that get the same color shirt on all their alts, although it's hard to see under all that armor. Some people like to take the same leveling path every time (like me), some people like to shake it up.
I even know someone who's leveled the same class to 80 several times - Warrior no less. But Rossi is widely considered to be crazy.
If you have alts, is there anything you always do the same way across all of them?