I have also made it a practice to keep a Purell pump on my table during rehearsals. Now that we're in show time (opening tonight!) I count on them to wash their hands in the dressing room, and have moved the pump down to the dressing rooms so they can use it. We haven't been hit by flu yet (knock on wood) but we have had a few people with coughs/sneezes, so I also make sure there are tissues on hand at all times.
Beyond that, I'd agree with BalletPSM. Wiping down props, railings, door handles, etc with alcohol-based sanitizers is probably your best bet. Also, if there is any eating off of plates, glasses, silverware in the show, make sure it is all cleaned thoroughly before the show, and that only the actor eating the food is touching the food when possible, so there isn't direct ingestion of the virus.