I can't say I've ever given it any thought....I would just give it a once over with the sponge I'm using to wash the car with. I dont seem to have alot of carbon build up or muck it so I dont see a problem with wiping it with the sponge.
I simply use turtle wax chrome polish. I clean the tailpipe with some soap and water. After that you still see some roaddirt on them. I give it a good coat of polish and let it sit for a few minutes. Then with an old rag I polish them untill they are new again. Works like a charm for me..