How To Optimize Adbrite for Publishers?

I would like to know the secrets for optimizing Adbrite for Publishers. I have a few different sites with Adbrite and if there is any way I can tweak my earning I would love to know it. Please let me in on any tips you know!
One thing in particular I would like to know about is the approval / rejection in the "Ad stats" of each zone. What kind of ads should I reject and which ones should I approve in order to get a better cpm? Also will rejecting many ads, (which in turn will leaves few ads) possibly render my zone ad free? For the record I currently have my ad settings to auto approve.

Original post by JasMate