My sister has a few, and I have a bit of basic knowledge. First off, they should be kept in pairs. Unneutered males will produce an oil that makes their heads look bald. You need to feed them fresh fruits and veggies, and they are nocturnal and sleep most of the day. You'll need a place AWAY from your bedroom to keep them as they can be a bit noisy. You also need to spend a good amount of time bonding with them, and it helps to have a little indoor tent in which to interact with them. Not to mention little pouches for them to sleep in, and carry them in.

Well that was a babbling collection of my thoughts... I hope that helps a bit.