Before I got my current litter box (holds 35 pounds of litter...thank goodness the farm store sells own-brand litter for $4 a 25-pound bag!) I used two rather large boxes, about half full, and scooped them out every night. That, however, is for adult cats. For kittens, you ideally want a shallower box so they can easily get in and out, and I've heard it recommended to use only non-clumping litter for young kittens, I suppose so they don't accidentally ingest it while they're still properly figuring out how to clean themselves. It's also recommended, at least by the shelter here, to scoop a kitten box three times a day.
You're supposed to have one box for each cat, plus one extra, but honestly I just find that incredibly wasteful and darn near impossible to actually do. Especially as you're not supposed to put them all in one place!