Hi Daryl,
I assume you are doing PPC for affiliate program, not your own products?
It sounds like you are asking for strategy rather than a paid tracking solution but...
A company that recently called me for a consultation has a VERY interesting solution
to the question of "which keywords are bringing me sales and which ones are just sucking my money?" KeywordXRAY - XRAY Vision for Keywords
I think if I was doing PPC for affiliate programs I would be using something like this to track and optimize my campaigns. If I was making 10K or more a month at PPC and was working blind because I didn't know what was working - well it seems this could boost results by a large percentage and for the 47 a month cost, it seems like a no-brainer.
The things that is VERY cool about this program is it will tell you which keywords made the sale without you having to get all your merchants to add a special tracking pixel to their cart, which lets face it merchants just arent going to be adding a separate tracking pixel for each affiliate that wants one.
This is not probably what you wanted to know but it just seemed the fit the question.
Disclaimer: I have not tried the product and am not endorsing it, just sharing the info. FOR NOOBS I would not recommend investing in a tool like this until you learn the basics of PPC and start to make some money.