Google AdWords content network is a endless source of targeted traffic. In fact, the clicks usually cost less than the search network which makes it easy to make money.
CPC vs CPM
When the content network was first launched, you were require to pay based on CPM (cost per thousand) instead of CPC (cost per click). Once it changed to CPC, more people jumped in to test it out & I was 1 of them!
Due to the fact that content network delivers a lot of impressions, many people were afraid to pay on a CPM basis because impressions does not means you get clicks. So many of us were so used to paying by CPC instead of CPM.
Improving Traffic Quality
Always start your campaign on a CPC basis, for the first few days or even weeks, keep running your reports within your AdWords interface to filter out sites which are giving you lots of impressions but little or no clicks.
Simply by removing them, your impressions will go down, your clicks should remain the same.
This will cause your click through rates to go up which results in lower cost per click.CPC To CPM
Once you get to the point where your click through rates are really good, switch over to CPM. Then calculate the cost of clicks by taking your total number of clicks divided by your total cost. If it cost less then continue with CPM, if it cost more, switch back to CPC.
You should see your click through go up once you switch over to CPM because for CPM, your ad may show up in a bigger size than when you are doing CPC. When you have a bigger ad, you naturally draw more attention & get more clicks.
Summary
Everything is dynamic, nothing is written on stone. Test out content network with CPC, switch to CPM & compare the difference, then just do whatever that makes you more money.
Google AdWords - Content Network Strategy