I have a 2 year old Diamondback bike with gears that have already rusted while living in the desert southwest. I'm not sure how or if they can be cleaned. Also, was something I should have done to keep them from rusting? Any advice would be helpful! Thanks
By "gears" I assume you're talking about the rear sprockets, or perhaps the smallest front sprocket, since they're about the only "gears" that are made of steel. And they shouldn't get rusty if properly oiled.
A little rust won't hurt the sprockets. Just oil the chain with good chain oil and it will transfer to the sprockets fairly readily -- the rust will wear off with a little use. More worrisome is the chain itself, since a little rust can hurt a chain, causing "frozen links" and accelerating wear. Again, oil it with proper bike chain oil.
It depends how rusted they are.
If it's just surface rust, then my answer to both questions is the same: oil.
Lots of folks like high tech lubricant sprays, but since you seem to be a low maintenance person I suggest to give everything that moves some auto engine oil, so that it has a good, sticky coating. The regular oil you use should be light machine oil, such as sewing machine oil.
Give those rusty parts a rub with an oily cloth; you'll probably find it mostly rubs off.
Make sure you move everything that is supposed to move, several times, so the oil gets in between those moving surfaces.
The reason most people would not use engine oil is that being sticky, dirt sticks to it.
As with any maintenance issue, if in doubt get it checked out.