Leveling monsters

[Eaglejarl]

I would like to have a RAW system for how to level up monsters -- both so that newly met monster could have more HD and so that ongoing enemies can continue to keep pace without just magically going "ding!" Every time the players do. (No offense, Crystal!)

Are there any such rules around?

[HunterOfJello]

Advancing monsters has its own section in the back of the MM. There are also sites online that will do it for you, though they're often limited to the monsters from Monster Manual I.

[Studoku]

Urpriest's Monstrous Monster Handbook (http://www.giantitp.com/forums/showthread.php?t=207928) explains this better than the MM does, along with a lot of other useful info.

Post 5 specifically has what you're looking for.