First clean with kerosene to remove grease and grime build up with a scouring pad to give some 'cutting action', then use something like a "CLR" Calcium, lime and rust solvent (use gloves as strong chemicals). After that you'll find the spokes are shiny stainless steel (only 306 - hence slight rusting that CLR removes) and alloy will be bright again. If not burnish it with a wet scouring pad and should look great.
Bigest problem is grime and grease from hands and road. Handrims get bashed up really badly but can be powder coated but forget paint - not tough enough. Easier and often not much price difference to buy new hand rims.
Pop out bearing and replace if any gritty noise when separately turned slowly by hand. Can regrease with SMALL amount of Moly grease if you pop seals off carefully, but usually not needed.
New tires and you'll have new looking wheels. To keep clean, try sugar soap every couple of months just brushed on then hosed off to keep greasy grime off.
Best of luck or buy carbon (mine are Karma) wheels that are really easy to clean...
Edited by COOL Mobility, 27 February 2010 - 09:42 AM.