After being on the adsense programme for many years, I have made one simple conclusion:
Targeted traffic is the key to driving up your adsense earnings.
The difference between traffic and targeted traffic
When I talk about targeted traffic, I am not just talking about mere traffic or number of visitors to your site alone. I really mean targeted traffic. Normal traffic is akin to your usual or loyal readers who visit your site and are just about willing to read whatever trash or gems you post on any particular day. They land on your site because they are probably bored at work, or are just surfing the internet. There is nothing that they are looking for in particular.
Targeted traffic on the other hand refers to the visitors to your site who are LOOKING for something. They might have stumbled upon your site through certain search engines or a friend might have shared your site with them because they found certain information that was really useful and just wanted to pass it on.
Based on my analysis of my ad performance, I was surprised that some of the rather random posts that I have written were actually the ones where the ads did particularly well. And I realised that it also happened to rank highly in the search engines for particular keywords. This means one thing: the people were looking for something and that drove them to my site. That is targeted traffic. And if one needs to write content, make sure that you write it for a particular group of people. Who is your targeted audience? How old are they? What are they looking for?