Tracking channel performance

Channels are something that you definitely need to setup for monitoring your adsense performance. There are 2 types of channels provided by Google:

Url Channels - as its name suggest, this type of channel is on per url (or more accurately, per url pattern) basis. You can setup a channel to monitor the performance of a particular page, or a group of pages under a folder.
Custom Channels - for this type of channels, you have to assign them unique channel names. When you create your ad src code, you can specify which custom channel the ad should associate with. The custom channel name will then be included (as the google_ad_channel variable) in the final ad source code. This type of channel provide a finer gain of monitoring.

So, how can channels help you? By tracking different channels' performance, you can have better idea about which types of ad (e.g. skyscraper, banner or large square... etc), what color scheme and which ad position works best for you. You can also spot out problems more easily, e.g. pages with low click rate may indicate irrelevant ads appearing, pages with low EPC may due to MFA ads... etc. Try to setup some channels and pay attentions to the statistics. Take corresponding actions when you spot out problems; you will see your adsense revenue improves afterwards.