depends how you intent to have them used / activated and what point you wish them to come on.
The easiest and probably safest power source (and where I would aim if I was to fit them) would be to tap into the feed from the back of the cigarette lighter in the arm rest / console, or if there is a 12v feed in the glove box, I can't remember?
Old fashioned courtesy lights were just a simple capacitor discharging through a bulb or two, but I don't think the modern setups are, they're controlled by the body computer and get well annoyed if you try and replace with LEDs, so wiring it into the courtesy lights could be a bad idea.
so big question is what you want them to do?
if you want them to run just whilst driving then that is simple, just jump em off the back of the cig lighter, but test first it does switch with the ignition.