The trend worldwide is to use fewer initial capital letters in headlines and titles. The two prevalent styles are both correct.
Maximum capitalization means capitalizing all words except tiny or unimportant words like to or of. This style makes a document or web page seem more formal, conservative and traditional.
Maxi-caps: 'The Bestselling Guide to English Usage'
Minimum capitalization gives initial capitals only to words that normally have them, such as the first word and names of people and places. This style gives a more informal, modern and relaxed impression.
Mini-caps: 'The bestselling guide to English usage'
How to choose the right style of capitalization
Your job as a writer or editor is to use the more appropriate style, and use it consistently.
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