Understand the difference between total revenue and net income. Most income reports tout total revenue. Net income or profit (what really matters) is often buried in the post. I came across an income report recently with a super impressive number in the title (and Pinterest image). It was total revenue. Not until I read the whole post did I learn this blogger spent well over half their total revenue on Facebook Ads alone. On top of that, they had an extensive list of expenses. By the end of the post I realized I had netted more than they did the previous month.

This is the strategy that most bloggers start with when looking to monetize their blog. However, keep in mind you're not limited to selling banner ad spots (which is generally an ineffective strategy these days). Consider other areas you could rent out: space on your pop-up box, social media headers, the "P.S." on your email newsletters...think outside the box (quite literally).
Lets say, for example, that you refurbish and resell used smartphones out of your home. You could use a blog to attract visitors to your website where you list your current phones for sale. Your blog might cover topics about DIY refurbishing. On one level, it seems counterintuitive because you want people to buy your phones, but it also helps you build a brand and gain recognition. Social media guru Jay Baer explains the concept on Copyblogger:
People who start to blog always thing of making money which tends them toward failure. In my opinion bloggers should choose the topic which interests them. They don’t think about making money. It’s about knowledge, try to learn more and don’t think about money stuff. There are many top blog topics to make money online but you can get success only with the topic you like to write on. Try to choose your topic for the blog. Making money is very easy, don’t think about it much.
Write content. I like to write an article from beginning to end with no breaks. It may take me an hour to write an article or I may be at it all day. Sometimes, content does span a few days, but for the most part, I like to finish a piece of content in one sitting. I then hand over the content to my editor to fix anything from grammar, punctuation, to the general flow of the article. The only thing she doesn't edit is my monthly income report.