It's Forensics season again and I just got back from a meet, so my head isn't very clear right now. (I managed 2nd out of 5 competitors in extemporaneous.)
Anyway, today I'm simply linking to Brandon Sanderson's Laws of Magic, along with my extrapolations of the Laws as posted over the last few months.
First Law---Magical Resolutions
Second Law---"Illegal" Magic Systems
Third Law---Expansion Versus Addition