Another way of making money from your blog is by being paid to write a post about a specific company, product or service.
For obvious reasons, advertisers won't pay someone who has only just started blogging, and the various intermediary companies who bring together the advertisers and bloggers - or publishers, as they are referred to - usually have an approval system before you are given the opportunity to write sponsored posts.
Usually, they will want the blog to be 2 or 3 months old at least and with a minimum number of total posts and/or monthly posts.
Once you do start writing the paid posts, then I think it's important to maintain the overall quality of the blog by writing about products that are in keeping with the content of the site, and also don't detract from your regular posts. This will, in the long run, produce better results both for yourself and for the sponsors.
Here are some sites where you can apply to write sponsored posts or reviews.
Pay per Post