Years ago, my wife and I were having dinner with another couple and he told the story of his new wife, wanting to do something nice as a surprise for him, who took all his sockets, wrenches, and ratchets into the bathtub and gave them a bath with soap and water. He did not endorse this procedure and neither do I. Like most previous posters, I have always wiped my tools with a clean rag and put them away after use. On those rare occasions when I have got greasy gunk down inside a socket, I have used kerosene or a shot of brake cleaner, or my parts washer. For plain steel tools that have been used and abused over the years, I like to use a fine wire wheel and then the buffing wheel if a shiny finish is appropriate. Otherwise, after the wire wheel cleanup, I use either flat black paint or rust converter to bring the tool back to life.