If you are using the rattle can chameleon paint from checkers/pep boys that kind of thing, do not use the clear coat! Also, remember to apply in reverse order of what it says on the can. I think it says base, color change, clear. The body is your clear coat, color change then a back up color.
For masking, I find that electrical tape works really well, it keeps a good seal on edges. I find cutting the body mount holes before painting helps a ton.
As was said before, with metallic/candy colors, a backing must be applied. White will give the color a bright color, silver will give it a pearl/metallic flake color, and black will provide a dark dark candy color. When I did my candy blue backed with black, I did a light coat of silver before laying down the black, to lighten the color slightly.
Oh, and if you do multiple colors, accentuate the body's lines. A poor masking job/paint theme can ruin a body.
