When writing out titles, there are a few capitalization rules you should keep in mind. I do want to point out that a few style guides only require the first word to be capitalized. For most others, these are the basics:
- Always capitalize the first and last word of a title no matter how insignificant or short.
- Capitalize all verbs (including be, is, are, was, were), nouns, pronouns, most adverbs, and adjectives. Many grammar books simply call these “significant” or “important words.” If it seems important, it’s probably capitalized.
- Do not capitalize most short words: coordinating conjunctions (and, or, nor, for, but), articles (a, the), as, to, and most prepositions—unless they’re the first or last word. However, the you-knew-it-was-coming exception is . . .
- You can (and probably should) capitalize any word that’s six letters or longer (some people say five), no matter what kind of word it is. For example, prepositions such as through and underneath can be capitalized because of their length.
- Do not capitalize words that have to be lowercase for another reason. The main place you’ll need to know this is with the scientific name of an organism. When writing them out normally, you capitalize the genus and lowercase the species (e.g., Yersinia pestis). Do the same in titles.
As I mentioned, these rules are not universal, though they are common. You should always do some research on what a particular journal, publisher, magazine, or website expects if you’re seeking publication.
Update (9/20/10): I should point out that some style guides recommend not capitalizing be, is, are, was, and were because they are linking verbs. I find this argument to be weak, since other linking verbs are capitalized (for example, seem). However, refer to your style guide for the final determination.