capitalization - Which words in a title should be capitalized?

Are there any concrete rules that say which words (parts of speech) in a title should start with a capital letter? What would be a correct capitalization for the title of this question?

Answer

This Writer's Block page on capitalization sums up the rules in one page which is the most useful that I have found, basically these rules from the Chicago Manual of Style plus a number of minor rules which are worth reading:

1. Always capitalize the first and the last word.


2. Capitalize all nouns, pronouns, adjectives, verbs, adverbs, and subordinate conjunctions ("as", "because", "although").


3. Lowercase all articles, coordinate conjunctions ("and", "or", "nor"), and prepositions regardless of length, when they are other than the first or last word. (Note: NIVA prefers to capitalize prepositions of five characters or more ("after", "among", "between").)


4. Lowercase the "to" in an infinitive.