If you do academic writing, then you’ll find this article interesting: When a Rose Isn't 'Arose' Isn't Arroz: A Student Guide to Footnoting for Informational Clarity and Scholarly Discourse, by Prof. William B.T. Mock, Jr. Professor Mock describes three kinds of footnotes serving three different purposes:
- Reference footnotes, citing the authorities supporting the text.
- Factual footnotes, providing background facts that the reader may not know.
- Idea footnotes, placing the writer’s arguments, opinions, and analyses in a broader scholarly context.
He then describes the proper use of each kind of footnote and gives pointers for writing them.
In a footnote near the end of the article, he gives a valuable pointer that every legal researcher will find useful: When photocopying something from a book or a treatise, always photocopy the title page, both front and back.1 Later, the photocopied title page will give you all the information you need to cite the work, saving you a trip back to the library for that information.
1 If you want to save a fraction of a tree (a twig perhaps), photocopy just the front of the title page, and write on the photocopy the most recent copyright date from the back of the title page.