According to most English style guides, titles of books, publications, and works of art should always be capitalized—for example, What to Expect When You’re Expecting, The New York Times, There Will Be Blood. Use up-style capitalization in these cases; that is, capitalize the first letter of the first and last words and of all words besides short (fewer than five or so letters) articles, conjunctions, and prepositions. Short verbs, nouns, and adjectives are capitalized; for example, in There Will Be Blood, Be is capitalized because it is a verb.
As for whether to use up-style capitalization in headlines and titles of articles and other short works, it’s a matter of editorial choice. The New York Times capitalizes article titles (e.g., “Hopes Dashed, Protesters’ Anger Spills Over”), as does the Wall Street Journal (e.g., “Egypt in Chaos as Mubarak Refuses to Go”). These two prestigious U.S. papers are in the minority, however. For example, The Washington Post does not capitalize (“Mubarak cedes some authority but refuses to quit”), nor does the Los Angeles Times (“Mubarak speech turns elation in Tahrir Square to anger”). Most British, Canadian, and Australian papers don’t capitalize—for example, The Guardian (“Fury as Mubarak refuses to stand down”), The Globe and Mail (“Defying expectations, Mubarak refuses to step down”), and The Sydney Morning Herald (“Saudis vow to support President if US stops aid”).
Outside news publications, capitalization of smaller works, such as web articles and blog posts, happens more often than not. The same is true of headings and subheadings. Most style guides recommend against up-style headings for such purposes, but try telling that to the average blogger, corporate report writer, or marketing copywriter. Non-professional writers love the up-style heading—and who’s to say they’re wrong?