SPC Libraries have copies of the book A Short Guide to Writing About Art (Author Sylvan Barnet).
This book is an excellent resource that has basic questions to ask when you are conducting an art analysis.
It also has specific suggestions for writing about: painting, sculpture, photography, and more including vantage points, the importance of lines and shapes, color symbolism, etc.
A catalogue raisonné is a comprehensive, annotated listing of all the known works of an artist either in a particular medium or all media.
Online Dictionaries and Encyclopedias are great sources of background information.