The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
Capitalize names of people, places, companies, departments, and geographical features. Whether a word is capitalized depends upon whether it is being used as a proper noun or simply as a common noun. In titles and headings, capitalize the first and last words and all other words except articles, prepositions, and conjunctions.
In headings and book or movie titles, capitalize the first word, last word, and all other words except articles, prepositions, coordinating conjunctions, and the word “to.” Various style guides prescribe additional rules.