I've worked at internships and student jobs at seven or eight museums. If you want some specific answers, I'll need some specific questions. But I'll write you some tips I found useful.

Do: Have an idea of what you want to get out of the experience. When you go in to talk with the museum staff about a potential internship, bring an idea of what skills you want to pick up, or types of projects you'd like to work on. Don't be afraid to speak up here. I know interns who don't do this, and get given busy work for 6 months.

Don't: Expect a full time job at a museum from one internship. I've got a Masters degree and nearly a decade of experience, and its still hard finding full time work.

Do: Talk with the staff before you agree to an internship. Make sure it's a good fit for both of you.

Don't: Be afraid to get your hands dirty! You're doing a collection internship, but they're short staffed for a program? Working in education, but the collection storage room floods? Volunteer to help out, and learn from an entirely different department.

Do: Have fun, but be professional! It's a terrible career field for those without a sense of humor, but we also get our work done. Us museum folk are an interesting bunch.

Hope that helped! Feel free to ask more questions as well!