Kind of depends on how dirty they are... but just a wipe down with a glass cleaner and a coat of wax can do the trick...

Or.. there is a cleaner called Novus 1-2-3 that does a nice job if you need to rub out any minor blems...

Or probably even a very slightly damp cloth followed by a light wax....

I typically remove all the hardware and give it all a buff up with a chrome polish.. followed by a light oiling... then I clean the shells real well.. and put it all back . Now typically for me has only been the 4 kits that I have owned.... there are a bunch of people out here who have done this 100's of times that might have better recommendations.. but that is my two cents.