How do you paint over a vinyl tile floor?

I have a shabby looking commercial vinyl tile floor. Kind of stained and dulled. I heard somewhere that you can paint over it. How do I prepare it so that the paint will stick?How do you paint over a vinyl tile floor?
Sand down any high spots and wash well. Use a high adhesive primer, and then a very good quality paint. If you want, seal with poly. Water based doesn't change color.