It's a matter of "house style", Daisy. I tend to follow Oxford (UK) style, which states that in titles of books, films, etc. only the first word and any proper nouns should be capitalised. We generally go in for far fewer capital letters and full points (periods) than our American cousins.
You may be interested to know, however, that Oxford also prefers -ize verb endings, though also accepts the use of -ise, which is far more common in British than American English.The thing is, if you use -ize you have to know when not to: we never use -yzse in verbs like analyse, and there are verbs that always have -ise: those ending in -cise, -mise, -prise or -vise and when the verb corresponds to a noun with s in the stem, like advertise and televise.All of which is why people tend to take the easier option and use -ise everywhere.
Oops - mustn't get too carried away! I could go on for a long, long time on this subject.