For argument’s sake, these are in proposed order of importance. I’ll be adding items as I discover them. Please send suggestions and comments.
Serrell, Beverly. Exhibit labels: An interpretive approach. Rowman Altamira, 1996.
Please don’t write a label without reading Serrell’s book from cover to cover!
This publication has only six pages of information on “Label Design and Text,” but if you are looking for a basic source to cite during internal disputes (“No, we can’t expect visitors to read something in 12-point font mounted 80 inches off the floor,”) or an explanation of the difference between legibility and readability, this is your go-to source.
Ravelli, Louise. Museum Texts: Comunication Frameworks. Routledge, 2007.
If you are serious about knowing all there is to know about writing for museums, you need to read this book. Ravelli is a linguist, and brings a different approach to understanding labels than many of the writers you may be familiar with (e.g. Serrell, Rand, Bitgood). After reading about lexical density, grammatical intricacy, and crystalline complexity, you’ll never look at a label—or any other writing—the same way again.
This guide is especially useful for label writers at curatorially driven institutions (such as history museums and art museum as opposed to science centers and children’s museums), but its before-and-after examples are useful for any writer. See my blog post for more.