Dish soap . . . probably as good as any.
I personally don't like any of the commercial cymbal polishes (Zildjian, etc.) because they tend to change the tone of the cymbals, and usually for the worse. This especially true when trying to shine up old cymbals. Like any polish, your esentially removing the top layer of material.
Now, if we're talking a few fingerprints and stick marks, I like to use those Dupont micro fiber clothes. They trap the oils from your hands and other dirt without any cleaner or liquid. Do this after you play everytime (takes about a minute) and your cymbals always look good as new. They also work great on drum shells and will never scratch your finish.
