Seams they beat me to it :P
At any rate you want a firm grasp on magic through meditation. Strong, inward and outward breaths with Pot belly (do not inflate your chest, but your stomach) breathing. I could go on and on about mudras and such but, I really don't think I could get to the other points.
Also understand magic does have limits (you wont get any hollywood cues and such.)
I wish you luck ^-^ ide reccomend you also read up on it first. An excellent book would be The Goodly Spellbook from Coven Oldenwilde, but theres many more im sure.