Steps to get the internship: I emailed the director of the museum with my resume and cover letter, and then had a phone interview.
Day-to-day activities: I sorted through old maps (from 10 to 160 years old), old postcards (most were about 100 years old), old print publications about northern Michigan (about 80-50 years old) and created an archival system and catalog for the maps, postcards and publications in the museum collection. I also made a finders' list for researchers to find the material that we had available at the museum.
Most rewarding: Being able to have a hands-on experience with items in a museum collection was very rewarding, especially when I found our copies of the first survey map ever made of Emmett/Charlevoix/Cheboygan county by John Mullett from the 1840s (Mullett Lake is named after him).
Biggest challenge: It was tough to remind myself that the class credit I was getting for the course was worth doing the work, because I wasn't being paid for the 130 hours I put in over the summer.
Most important thing learned: It's very important to communicate with your supervisor if you don't understand what they want before you make a mistake. Also, being able to work autonomously is extremely helpful in a museum environment.
Key advice: Do it! But make sure you know what you want to get out of it. I did my internship because I needed an internship for my Museum Studies minor and because I wanted to see if I really liked museum work. I also knew I'd be able to have a lot of hands-on experience working with real artifacts because it was such a small museum, so make sure you will actually be doing what you want to know, not just some side projects or busywork for interns that the people you're working for want you to do.