Read a blog tonight about magic. The author had attended a conference and she shared some of the highlights. http://leigh-covington.blogspot.com/2012/02/abracadabra.html
The first - magic has to have a purpose and drive the story.
I think most sane people know you can't write a story solely based on magic. Harry Potter had lots of magic in it, but it was the characters who drove the story.
That's what I like to do with mine - have the characters drive the story.
I don't spend a lot of time explaining the magic or how it works. It's just there... at first, my character is surprised by it. She's never had it before, but things happen, and now she's got it. Part of the story is the learning curve, but so much in her life has changed that the magic seems a distant blessing.
Survival is of the utmost importance. If she can use magic for her survival, then well and good. However, she's got no time to explore that new part of her. And she's got a brother to save.
So the magic is there. I don't want it huge. I want it peripheral. I hope that works.
Life is magical.