It all depends on the effect you want to achieve. I usually use 3 colors.. but that's just my preference. I have a tutorial and that's one thing I talked about. If I have a fabric I want to stay in larger chunks I put that in the 4 corners. the 4 "side" blocks will end up being strips. and the center block will end up being cut into quarters. Here's my favorite D9P..
http://i778.photobucket.com/albums/y...Picture062.jpg