This post in AdSense optimization series will help you maximize your earnings with "DoubleClick Ad Planner," that help you market your site, make it easier for advertisers to search for you, and improve the data that these advertisers can see.
The first step to enabling placement-targeted ads is to set up custom channels as ad placements. Ad placements are specific groups of ad units where an advertiser can choose to place their ads using placement targeting. Turning custom channels into ad placements is simple. Watch the video below or visit Help Center.
Once ad placements is setup, try out Ad Planner, where you can claim the sites you own and customize descriptions. For each site, you can also add up to five categories describing site's content, and types, sizes, and formats of ads that your site supports. Doing this allows advertisers to easily find ad placement descriptions that match the interests of their target audiences. More targeted ads leads to a better user experience on your site and a greater opportunity to increase your earnings.
Watch the video below for more info, and sign up Ad Planner, if you already haven't.