I bet you are thinking this is too simple and couldn’t possibly work to generate an income, well the fact is people view blogs of interest and since they will be doing this, you want to have blogs out there they are viewing with ads that will interest them, so they have the opportunity to click you ads and earn you money.
The truth is people are hungry for information and they search the internet for it, if they are on your blog, the chances are they were looking for the information your blog supplies and if that is good information they are more likely to take a look at the ads you have running on your blog for related information. If they like the sites that you earn commission from enough to buy, then they get a great problem solving product and you get a commission for connecting someone with it, so everyone is happy. Below you can see a few blogs I have running in different niche areas of interest, so as you can see I do not focus on one area.