If the house staff haven't taken care of it, research how the house phones work, and post a short list of emergency directions by any exposed phone. In particular, find out which number the theatre uses for external numbers (usually 9, but it can vary), and whether or not this applies to 911/your local emergency number.
You should post:
- The emergency number ("For emergencies, dial 9-911")
- If available, the number for building security
- If available, the number for the house manager's office
- The facilities/maintenance number (For those "We have a show in two hours and the women's dressing room is flooded!" situations)
- The technical director's number, if their contract/understanding with the company includes ongoing maintenance and emergency response ("The set fell over during our lunch break! What do we DOOOO?!")
- At the very bottom, your own number
In all cases, keep it simple. I would encourage you not to provide general-use directions (You don't want to encourage company members to use these phones except in emergency situations, so leave off instructions like "For local calls, dial 9 before the number." and focus on specific directions: "To contact building security, dial 45000. To contact the house manager, dial 30000." etc. etc. etc.)