Magic in my game works how people think magic in the real world works: in TONS of different ways.
Voodoo practitioners approach magic differently than medieval alchemists, new age mystics, religious evangelists, or baseball players. (You don't think they're superstitious? Watch the routines they go through as they come up to the plate.)
If you think magic requires strict logic and a scientific approach, then that's how magic will work for you. If you think magic depends on belief and faith, well, when your faith falters, magic won't work anymore. If you think that you're special and that the world bends to your desires, then you're egotistical *ss, and you'd better keep a high self esteem when you go to fight Tiamat.
To accomplish this, though, you either needs tons of classes, one for each culture or mindset on magic; or you need a more flexible magic system, with templates that you can apply to represent how your Nordic rune magic is different from that kid's magic which he just made up because he watched lots of anime and thought it looked cool.