For the content network you definitely want to be aiming for a CTR higher than 0.10% - some of my campaigns are up to 1% so it definitely possible. Getting a higher CTR will mean you can increase your volume and decrease your avg CPC.
You also want to be monitoring what percentage of people clickthrough on your landing page. Personally I would be trying to get the reviews of the products higher on the page - maybe only have one paragraph and then get intothe reviews?
Generally I spend the amount of the payout on the offer before looking into what keywords are doing well. After 3-5 times the offer payout has been spent and I have no conversions I generally kill the campaign - depends on the niche though.
Programmer, web developer and entrepreneur.