What's the size of the artwork, and are you shooting digital or film?
The really professional way is to get a copy stand, but that's expensive. I use a music stand, the kind you find in most colleges (manhasset). I set up 2 shop lights, one on each side just out of view of the camera and blanket the artwork in as even a light as I can, put the camera on a tripod, use mirror lockup, and shoot at f/8, usually with a 50mm lens or longer. If you are shooting digital, do a custom white balance before hand by setting a piece of white matteboard on the stand. If you are shooting film, you'll need a color compensating filter, or tungsten balanced film to compensate.
If you have an overcast day, you could take your setup outside and use natural light.