I have always heard that there should be one box per cat. I have chosen to go that route most months but in the summer, leave on huge box on the porch (screened in) so that I don't have to smell the nasty odor in a non-air conditioned room. It seems to work for them.

I usually buy storage containers rather than litter pans and make my guys leap into them. They seem to track less litter outside the box that way.

Right now I have three boxes going. One in the kitchen, since little Ms. Chloe was digging around in a spot that looked appealing to her....rather than ruin the carpet, I put a box there. Now all three cats love that box. It is under a chair.....near a corner.....but ewwwwww, the stink is horrible when they use it. Oh well. Cats.