Title case is the way that the capitalisation is done for titles of things like songs, books and articles. Having had a hunt around, there doesn’t seem to be a good definition on how it should be done. Wikipedia describes a range of rules but doesn’t come down in favour of any of them except to say that it is not fashionable among publishers. Even so, if you are producing, say, a list of albums and songs for a media centre then it looks a lot better if you are consistent and, as the article points out, it is easier to automate rather than using sentence case and trying to spot the proper nouns.
The best rules I can come up with are…
- Start with a capital.
- Capitalise after spaces but not other punctuation.
- Don’t capitalise any one or two letter words (except I) nor certain three letter words:—and, but, for, the, via & others for foreign languages (e.g. les, des).
- Like all good rule sets there are always exceptions but these have to be done by hand.