What Do Editors Expect from a Title - Debbie Guzzi's Blog

Sentence case (also known as Down style)

Capitalize only the first word of the title and any proper nouns: "Rules for capitalizing the words in a title." This form, recommended by the Publication Manual of the American Psychological Association for titles in reference lists, is popular with many online and print publications. In fact it's now the standard form for titles and headlines in most countries--but not (yet) in the United
States.

Example: On the Pulse of Morning
by Maya Angelou

Title Case (also known as Headline Style or Up Style)

Capitalize the first and last words of the title and all nouns, pronouns, adjectives, verbs, adverbs,
and subordinating conjunctions (if, because,as, that, and so on): "Rules for Capitalizing the Words in a Title."

Example: On The Pulse Of Morning
by  Maya Angelou

It's the little words that style guides disagree on. The Chicago Manual of Style, for instance, notes that "articles (a, an, the), coordinating conjunctions (and, but, or,for, nor), and prepositions, regardless of length, are lowercased unless they are the first or last word of the title."