You can also create a spell that gives weakness to magicka on yourself, or some other debuff effect. I've been playing around some and I think the following spell types raise these schools the fastest:
Mysticism - detect life (maybe spell reflect/absorb do it better, I'm not sure, but I made a new character and got way up in mysticism with the basic minor life detection spell)
Alteration - shield spells (gained 30+ skillups casting "protect" which is a basic 5% shield)
Illusion - light spells (I don't know for sure, but this seems to raise it fast without any real effort)
Playing the game through again as a sneaky marksman assassin, and it's fun. But I'll admit I cheesed my way up to a high rank in sneak by finding some patrolling non-hostile creatures and sneaking into a corner while they ran past. Still, marksman isn't so bad so far - one thing I've noticed is you HAVE to buy the best arrows available, otherwise you're just not going to get as much damage as a melee type would. I kind of wish they had a better stock of arrows in the shops, though. It seems for me that I can buy silver/steel but they don't restock, while they do restock with iron.
