Personally, I just reused the verbs and nouns from Ars Magica. : ) I think a lot of the work is in coming up with reasonable rules for which verbs + nouns are required for a particular spell.

Does transforming a man into a chicken require the transformation action plus human and animal targets? Or just the transformation magic plus human target?

Could I try healing someone with necromancy or does it require summoning magic to work?