*Salutes Baldaren*
I also would recommend browsing the Official WoW boards (Realm Forums) as most realm forums (EU at least, rarely visit the US etc unfortunately) have a sticky at the top with guild listings that say what type of guilds are on the server, homepages, type of guild etc etc.. and is a good place to start. Guilds will also usually advertise their guilds, recruiting there too and is a great way to find out what type of guilds they seem to be from their recruitment/advertising posts... then you can perhaps contact the leader/officers and chat a bit about finding a Mage mentor?
one other thought - have you tried the Guild Recruitment channel in-game? quick way to find those who may be interested in offering a new, growing mage under their wing?
Good luck and happy adventures ;)
Edited, Jan 28th 2008 12:25pm by WoWard
Edited, Jan 28th 2008 12:25pm by WoWard