Depends on what stage they're at. If they're basically clean with only light surface corrosion showing, Autosol or any other automotive chrome polish will do the trick, as will Brasso or Duraglitz.
If you've got big rusty scabs, then some fine steel wool (don't use sandpaper) before the metal polish. If the chrome is really rusty, there is a mild rhubarb based acid (the name escapes me at the moment) which you can leave the parts in overnight and you will be amazed at how clean they come out.
a bit of the topic but Mrs R had a load of silver bracelets that had tarnished badly,she cut up some stamp sized bits of silver foil added some baking soda and water and then dipped the silver items in,The smell it produced was awful (like stink bombs) the silver items came out looking like new.