To summarize it in my own way, for ad sense to work these are the basic things:
1. Good niche
2. Optimized website
3. CPC of $1+ or low if the keyword generate not less than 5, 000 global searches monthly.
4. Traffic
5. Rinse and repeat..
Apply these tips if yuo wanna Growing your Adsense CPC..
He,he,he... Traffic!!!!
Do you know that recently big ads companies lowered payout from clicks in ads.??
If you have a very good site, focused on topic and with unique content, you are going to earn more by showing affiliate banners, very related to the topic of your site.
That's all folks! I'm going to make some coffee!!
If you are able to reach to hand-held or mobile readers than CPC may increase as ads shown on cellphones are of higher quality.
Experimenting can really pay you high dividends. You can try out for different niches, choose different ad placements and finally take as many as advice from Google adsense center
If your PR is 5 or 6 then Google will show ads on your site which will pay you higher if someone clicks on them. Simply it means that ads of higher quality will be more shown on your website.