Capitalizing of correctly is rather easy. Unlike many other words discussed in this blog, it has just one grammatical function: of is always a preposition, and all style guides are in agreement that (short) prepositions should not be capitalized in titles and headings.
Phantom of the Opera
The End of Eternity
State-of-the-Art Technology
There are, however, exceptions for the first word and last word of a title.
First Word
The first word of a title or headline is always capitalized:
Of Mice and Men
Last Word
Of can occur as the last word of a title. In such a case, its object occurs earlier in the title, and of is referred to as hanging, dangling, or stranded preposition.
Since AMA, APA, and Bluebook do not have a rule to always capitalize the last word of a title, of remains uncapitalized in such a case:
Nothing to Be Afraid of
AP, Chicago, MLA, New York Times, and Wikipedia however require capitalizing the last word of a title:
What Were You Thinking Of?
If the object of the preposition is missing completely though, and the title ends with an ellipsis, then of should be lowercased in each style, as explained in the article Capitalizing Titles Starting or Ending with an Ellipsis:
All in the Name of …
Check out this site’s title capitalization tool to automatically capitalize your titles correctly!
Photo: Renee Fisher