There is a huge volume of data available online that allows you to find out what your competitors are doing and get a good idea of what offers and approaches are effective. Though you probably already know your main competitors, a quick online search will help you discover many more - simply use the top keywords for your topic.
In looking at competitors in general, you want to know:
Think of anything you put up on the internet as a product. It doesn't matter if that product is an actual product sold through your online business or a fledgling blog about books and authors in your country. As a product, you want it to be seen (and, in some cases, bought) by as many people as possible. After all, if this isn't your intention, why put it on the internet at all?