6 April 2014
Publication titles follow different capitalization practices, according to the language in which they are written. English-language titles typically follow Headline Style, capitalizing all words except articles (a, an, the), coordinating conjunctions (and, but, nor, or), and prepositions. However, all these are capitalized when used as the first word of a title or subtitle. The casual practice of capitalizing long words and lower-casing small ones doesn't follow any style guide in existence. Sorry!
Non-English languages follow different conventions. French titles capitalize only the first word and proper nouns. German titles capitalize only the first word and subsequent nouns. For other languages, consult a style guide for that language. Using sentence-style capitalization, in which you capitalize only the first word and proper nouns, is a practical alternative for non-English titles.
Extracted from EE 2.60–62, which treats this subject much more fully.