There are many ways to monetize your blog or website. But the best way to monetize a blog is by contextual ads.
I have described the whole process below.
Advertisers select your website and ask you to insert their links at a desired part of your website. It might be within your post or in the side bar or any where. Once you do that they pay you monthly for keeping that link on your page.
There are many platforms available for doing that. But my favorite one is Magenet where the whole process is automated. Magenet has created a plugin for WordPress and Blogger platforms and once you install their plugin, the advertiser's link is automatically placed on your blog and you start getting your monthly payments via PayPal.
So, once you have added all your blogs and websites, you don't have to do any work. It is that simple.
All these work almost in a similar way.
Hope this information is useful and will help you find the best way to monetize a blog.