Increase AdSense Earning

1) I Removed Low-Performing Units

Low-performing units drive your overall click through rates down, which could impact how many AdWords advertisers you attract.
The 468×60 unit has always performed pretty poorly for me, so I’m not sure why I stuck with it for so long.   Perhaps it was because it fit well in that space, and I never took the time to try anything else.
Nevertheless, I replaced all of those units with a 300×250 unit and it raised my click through rate by up to .6% on some channels.
That may not sound like much of an increase, but my earnings for those units have been positively impacted since the change.

2) I Now Use Text and Image Ads

Image ads don’t always convert as well as text ads on my sites, but what I’m noticing is that I seem to earn a lot more per click (on average) now that I have enabled them on all of my units.
In the past, I’d only enabled image ads on some of my units.

3) I Changed the Text Ads to Match the Link Color on My Site

For awhile I was using a different color for the headline/title of my text ads.  The idea was to make the ads pop a bit.
This strategy worked great at first, but I noticed my CTR was starting to drop.  So I changed the headline to match the color of the links on my site.
————————————————
As you know, it’s impossible to prove exactly how much these changes impacted my earnings.  A lot may have to do with the ads that show up and some of this may be pure coincidence.
However, this is the time of year when my traffic is typically lower yet my AdSense earnings are higher than ever.  So I felt it was worth noting here on my blog.
These tips may not be ground-breaking, but they remind you how important it is for you to experiment and constantly monitor your channels. 
What works today may not work as well next month.  And what works for me, may not work for you.
Experimentation is key.