Placing ads on a Directory Site using phpLD Script

I know very well the revenue from adsense on directory sites are very low. Still would like to have some feedback on the best places to place the ads for maximum revenue.

The site uses the phpLD script. Should I place one horizontal unit in the header and one in the footer?

I would appreciate replies from those who are having good success in this regard.

Abhilash.

 

I think its better if you post the url of your site so we can give some ideas..