Affiliate sales comprise a large chunk of revenue for most big-name bloggers. For instance, Pat Flynn made $53K last month from affiliate sales, compared to "just" $9,500 from book sales. In general, look for affiliate products with higher price points; web hosting companies are a great choice if it makes sense in your niche, with payouts of anywhere from $60-$130+ per signup.
In other words, Jon is an incredible writer, communicator, and hard worker–no question. But you’re in the business of helping other people make money. You’re not, by contrast, a travel blogger. You’re not, by contrast, helping to teach people how to buy their first pet. You’re not, by contrast, an entertainment blogger writing about Rihanna and “True Detective.”
Once you setup your account on AdSense you will be given a code to add to your blog. This code will automatically display advertisements on your blog from companies who are part of Google’s advertising network. You may see ads from small companies related to your topic, or you may see ads from large companies that are completely unrelated to your topic.