What you've got are polished aluminum with a tough plasticized clearcoat -- similar to the clearcoat on your paint, but formulated a little tougher. This is the same coating found on painted factory wheels.
Wash them frequently with soap and water -- use a separate mitt for you wheels, tires and grungy stuff. Dry with a soft cloth.
Basically, keep them clean and dry -- they will stain, collect dust and they water spot, just like your paint.
Avoid harsh cleaners, like glass cleaners with ammonia, which will strip any wax protection. If you must use a wheel cleaner, rinse thoroughly with sudsy water and dry thoroughly.
Protect them like your paint with some quality wax -- I have found that after every wash, if possible, I'll do a final wipe on my wheels with FX Spray Wax sprayed on a microfiber towel -- it's easy to apply and helps to keep brake dust and other debris from bonding, making cleaning that much easier. I tried one wheel wax and wasn't too keen on it -- it was harder to use and didn't seem to protect as well.
If you need to polish, I find that Plastic Polish on a PowerBall Mini and my cordless drill works really good. | 
