1. Sentence Case
This style is where you capitalize the title like you would a sentence. You just capitalize the first word of the title and the proper nouns. Also known as Down Style.
For example: "Capitalization: do's and don'ts" or "It's Sally's birthday!"
2. Title Case
This is the style that I prefer. It's where you capitalize all nouns, pronouns, adjectives, verbs, adverbs and subordinating conjunctions (ex. if, because, as, that ect.), and the last word of the title no matter what type.
You don't capitalize articles (ex. a, an, the), coordinating conjunctions (ex. and, but, of, for, nor) or prepositions (ex."He fell off his bike") Also called "Headline Style" or "Up Style".
For example: "Capitalization: Do's and Don'ts"
It really doesn't matter which style you use as long as you're consistent. Although, I would recommend "Title Case" style. So go forth and capitalize titles properly!