Unless you're having drainage issues and everything likes to stay wet and stinky, you really don't have to do anything to the run, especially if you let them free range during the day. I would suggest if you rake up grass clippings and/or leaves, throwing them in there will give the chickens something to scratch around when they can't get out. Also keep and eye out for free stuff. The city often offers free mulch which is usually trimmed branches and fallen trees picked up after storms. Also my feedstore has no problem with me cleaning up the busted bales around their hay trailers every now and then.