Are there rules for this? Of course. Let’s look at our handy-dandy style guide and see what it says. For fiction, that would be the Chicago Manual of Style. There’s a rule in Chicago for just about everything. It can get a bit arcane (like so many things), but if you stick to the basics, it’s not so bad.
Here are the rules for “headline-style capitalization”:
- Capitalize the first and last words, and all other major words of a title.
- Lowercase the following words: the, a, an, and, but, for, or, nor, to, as
- Lowercase prepositions (even though they may be long words). For example, above, behind, during, inside, on, outside, throughout, until. This one is a little tricky, because when a preposition is used as an adverb or adjective, it should be capitalized. For example: Stay Outside for Your Health, or The Inside Story, or The In Crowd. By contrast, it would be The Ogre outside My Window, An Explosion inside the Chemical Plant, and Capitalizing Words in a Title.
- Lowercase any part of a proper name that would be lowercased in text, for example von Helsing.
- For hyphenated compounds, always capitalize the first element and usually the second unless it’s an article, preposition, or coordinating conjuction; if it is a spelled-out number, capitalize both.
Phew. That ought to cover the majority of situations. And in case you really don’t like the look of what these rules do to your title, none of this is set in stone. Even Chicago allows that titles may deviate from the rules for aesthetic purposes.
For more information, look up sections 8.155 and following in Chicago. Or see whether your issue has been addressed on their surprisingly entertaining Q&A site.
Or ask, below, and I’ll try to figure it out!