Magic in general is taught through training in an academy-type setting. We could assume that there are rare unexplainable occurences of people "knowing" magic at birth or other ways, too? Knowing everything about magic kind of takes the mysteriousness out of it so I say we leave the source of magic to be unknown.

I sort of have a "job" system set up that allows a pretty wide range of customization. You can point your character in a lot of different directions but the more you diversify, the more everything gets averaged out. It's really up to how creative you want to be, I guess. I think coming up with new types of magic would be really fun.