This post explains what I've learned about Google Adsense. It explains the figures like cpm, eCPM, Page CTR, and Earnings. DCE Started using Google Adsense early 2005. Up until the beginning of this year it's had very little success. The success increment is due to redesigns, studying, and experimentation. Below are 8 bits of information I wish I knew from the start.

1. Placement. People won't read ads unless they're practically forced too. I can't remember the last time I've looked away from content to read advertisements. Can you? My first site designs had Google ads running along the the left of right hand side (separated from the content or navigation). This was done with design in mind, it looked pretty because the nasty Google ads were at least 100 pixels away from the content at all time. Jakob Nielsen has a great study out on Screen reading eye patterns, its sums up eye tracking to an F-shaped pattern, read it.
2. Design. Don't try to hard. If you are apparently forcing the ads, not one will read your content. Don't use more than 2-3 adsense boxes a page. Break up the content with ads or put them before and after if you hate to sacrifice design and the content like myself.
3. Content. Content is king. Make sure your content is valuable, helpful, or informational. Check your time on site stats with analytics, if its low people aren't reading your content. I know there are quite a few out there that will reward good content by checking out the sites ads. Quality content will eventually earn you invaluable link ins.
4. eCPM. eCPM is effective clicks per thousand impressions. The number is a rough figure of what your site will make per 1000 ad impressions. Example: in March my page impressions were 1,153, my eCPM was $2.56 (made around 3 dollars that month) eCPM is a great way to gauge a new site designs effectiveness in a few days rather than waiting a full month. An average CPM $9-12, with my last redesign DCE finally broke into the average after 3 years of failure.
5. Page CTR. Page Click Through Rates is the number of clicks an ad receives divided by the number of times is is displayed. If you want to keep this number high consider using ad units with fewer ads displayed. In some instances you can control this in the ad unit options.
6. Ad Units. Yes, there are ad units that prove more successful. I've noticed the large square and vertical rectangle ad have the highest CTR on my site. The small ad links get decent hit, but the earning per adlink is very low. This being said it is site design specific, experiment, some ads will work better than others depending on your site design.
7. Statistics. Understand your stats, read up on analytics/adsense stats. Eventually you want to be able to read these stats like the Neo from the Matrix. Things will click and make sense ; )
8. Failure. You will fail, things wont happen over night. Personally I would focus on getting your page traffic up before you start advertising. A good goal is to get 500-1000 pageviews a month, this way you can read your eCPM fairly accurately.

Thats all for now, go get up. Please post comment on your experiences and I will append them to this list.