Although this essay is concerned with the writing of museum labels for artworks, it contains useful advice on keeping the knowledge level of the reader in mind.
"Discusses several common types of art history assignments, and talks about various strategies and resources that will help you write your art history papers."
British Museum curators discuss their favorite museum items.
Museum Catalogues Online
For examples of writing for art exhibitions, and to gain ideas on how to approach such an assignment, please see the digital catalogues from the following museums:
Wentworth
Institute of Technology