Where should I place the ads on my pages?

From Videoegg

Placement truly depends on the user experience on your property. Generally speaking you should place the units in highly visible, highly trafficked areas where users will naturally interact with them. Typically this means above the fold, towards the center, and closer to the top of the page. But every property is different and every page is different! You should experiment with a variety of placements to optimize your users’ experience and your earnings. The Banner for Facebook canvas pages, however, must be placed in a specific position. Please refer to the integration guide for more information.