According to Herbert Spencer, English philosopher, political theorist and lead singer for the Social Darwins, "The ultimate result of shielding men from the effects of folly is to fill the world with fools."
Nowhere is this more true than planet earth, and AdWords in particular.
19th century department store magnate John Wanamaker is credited with having said, "I know half my advertising is a waste of money. I just don’t know which half."
With AdWords, you can find out to the keyword, to the web page, to the ad, which ones are making you money and which aren’t. You can bid precisely to get the optimal position. You can discover that you shouldn’t advertise on Saturday afternoons, or in Wichita during college football games, or on any searches that contain the word "emanuensis."
You can discover all these things by setting up conversion tracking and analytics, creating and automating reports, and studying them on a regular basis.
Chapter 14 of AdWords For Dummies covers Conversion Tracking and Reports, and Chapter 15 features a wonderful primer on Analytics. (I know it’s wonderful because most of the content was provided by Timothy Seward and his merry band from ROI Revolution.) Until you’re munching on marketing feedback, you’re undoubtedly more of a fool than you need to be.