A quiet corner. Cats like to be up high so the inside of a drawer or on a shelf (that the kitten can safely get up and down) would be ideal. Honestly, though, whenever a new kitten joined our house, it always wanted to sleep on the humans' pillows, never in its own place.
A good place to put a kitten bed is a place where your cat likes to take a nap. Point out his/her favorite napping place and place the bed there. Other good spots include a quiet place, near your bed or near his/her favorite furniture. Get more tips from http://www.overstock.com/guides/top-5-places-to-put-cat-beds.
Put one down someplace above the ground, doesn't have to be ceiling high, just above the ground, and then watch to see if it uses it. If your kitten has decided there's a better place to sleep, move the bed there.
Cats like to be up higher to be able to see danger coming. The extra elevation gives the cat multiple avenues of egress from an attacker, but gives the attacker only one.
The cat will choose its own place to sleep depending on the weather. If it is cold, a cat will curl up on a bed with pillows or on top of a couch. If it is very hot out, the cat will stretch out on a table or kitchen counter.