Jenny points to a wonderful post at Museum 2.0:
1. Don’t use Twitter to spam me about visiting.
2. It’s okay if you start by just following.
3. Once you decide to tweet, make it interesting.
4. Tell me something I can’t find on your homepage.
5. Tell me who you are.
6. Respond to people.
7. Give me content worthy of your institution.
Great suggestions for sure, especially the bit about using to Twitter to share the museum’s humanity.