So here's what's in my toolkit as I develop simple prototypes (my work primarily focuses on history and art; science prototypes might be different). For me, prototype development tunrs my office into little piles for each project, as I play around and try and figure out what works. Because I am perhaps one of the most un-hand-skilled people in the world, it means even you can develop prototypes.
First--other museum colleagues. When I wanted to know what sort of bag would work best for families to use in museums, I queried the museum educators on Museum-Ed. Sure enough--great responses: clear backpacks, garden totes and even children's tool belts. I also found a great web resource from the Victoria and Albert Museum on designing family backpacks.
Mike Baird Photo at the Morro Bay Aquarium via FlickrWeb resources: Other useful web resources for thinking about museum interactives include the Family Learning Forum of the U.S.S. Constitution Museum and, believe it or, Flickr and YouTube. Searching for "museum interactive" on Flickr gives you more than 14,000 examples of what at least one person thought was an interactive worth documenting--and on YouTube--almost 5,000 videos. Thanks to Flickr I adapted a poetry writing template from the Denver Art Museum. (And, as usual, a big thumbs up to museums that allow photography and a big thumbs down to those who don't).
Senses and Intelligences: use as many as you can. Think of interactives to use all the senses. And I return again and again to thinking about Howard Gardner's work on multiple intelligences. If you don't already think about your interactives within that framework, here's a place to learn more and take a simple quiz about your own learning style.
Office and art supplies: nothing expensive but foam core, colored pencils, printable magnet paper and small magnet boards, clipboards, Post-it notes, felt, and of course, your printer to print out images and directions. Most of these are things that any museum educator has in a plastic bin somewhere for program use.
Ways to organize: Providing clear directions for interactives is one of the biggest challenges--how to make the directions detailed enough, but not too detailed. In this project, one challenge was making sure that visitors used the right activity in the right room. We used inexpensive translucent envelopes, labeled with the room name, color coded and accompanied by a map.