I used
Mage area of effect locations - WoWWiki - Your guide to the World of Warcraft as a reference point for decent AoE spots. It's tough going though especially in the early levels but at 22 you can get 3/3 elemental precision, 2/2 Imp frost Nova, 3/3 Permafrost and 3/3 Improved Blizzard which are pretty much the core talents you need to do it successfully. Good luck.