There are different ways one can go about capitalizing titles. What seems to be the most popular method is to capitalize every word, with the exception of most prepositions of three letters or less. It is the style I'm using and it is actually recommended by the much revered AP style guide. There are some variations on this theme, usually divided by the use of prepositions. Some don't even bother with this proposition nonsense at all and capitalize every single word in the title. I find this often leads to a slightly less sophisticated look, although when aiming for a more 'Millennial' crowd, that could actually be something you might look for. It is also possible to simply write down a title like you would any sentence. This has the obvious name 'sentence style'. There is also the possibility of not capitalizing any words at all, but that rarely comes off as professional, in my opinion. The flip side of that would be the 'all caps'. Where, you guessed it, all letters all capitalized. There is a definite place for such titles (especially in combination with sans serif fonts), but keep in mind that because capitalization also used for emphasis, the title might come off as 'screamy'. Unless you work for a tabloid magazine or a click-bait website, such an effect is probably not desirable.
Whatever style you choose, remember to stick by it. Nothing graces a page like consistency.
Below are a few examples of different types of title capitalization:
The Quick Brown Fox Jumps Over The Lazy Dog
The Quick Brown Fox Jumps Over the Lazy Dog
The Quick Brown Fox Jumps over the Lazy Dog
The quick brown fox jumps over the lazy dog
the quick brown fox jumps over the lazy dog
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG