Forum Moderators: martinibuster
First, welcome to WW and the Adsense forum!
Messing around with the ad formats and locations can affect your CTR as you've found out. Trying different colors can help in some cases. Using the rotating color scheme function might also help, it did for me anyhow.
EPC is probably harder to manage. That's going to be affected by Googles "smart pricing" of ads for advertizers. That means that about all you can do is try to write, or rewrite, pages that lead to better conversion rates for advetizers with-in your market site theme.
And your site demographics play a huge role. Lots of impressions will do you no good if your visitors aren't looking to do anything on your site except, for example, post messages (if it's a forum site.)
Do the ads you are getting seem likely to interest your visitors? If not, can you tweak your pages to improve the ad targeting? And if that doesn't work, and the other suggestions you will get from people don't help, maybe AdSense isn't for you. It doesn't work well on EVERY site.