Capitalization in Titles
In titles, do capitalize
  • The first and last words of the title
  • All nouns (e.g. man, bus, book, etc.)
  • All pronouns (he, she, it, we, you, they)
  • All verbs (e.g. run, eat, sleep, etc.)
  • All adverbs (e.g. slowly, quickly, quietly, etc.)
  • All adjectives (e.g. angry, lovely, small, etc.)
  • Subordinating conjunctions (as, because, that)
  • Any conjunction or preposition of five letters or more

As you have probably noticed small words are generally lowercase in titles, unless they are the first or last words in a title.
In titles, do NOT capitalize
  • Articles (the, a, an)
  • Prepositions of four letters or fewer (on, at, to, from, by)
  • Coordinating conjunctions (and, but, or, for, nor, etc.)

Sources:
http://www.yourdictionary.com/grammar/capitalization/rules-for-capitalization-in-titles.html
http://grammartips.homestead.com/caps.html