Google AdWords allows you to automate a great deal of your campaign management. One particularly helpful aspect to automate is keyword bidding. Joel Chudleigh has a great rundown at Business2Community of how to set rules in AdWords to ideally bid for and pause keywords, but I’ll give you a quick summary.
When setting your rules, simply consider what an optimal keyword performance for your campaign is. A keyword that gains clicks but no conversions would likely need to be paused, so set a rule that does so after a certain number of clicks without conversions.
What’s an acceptable average cost per conversion? Set up a rule that bids up any keyword that exceeds that average. You can also bid down keywords that are out of your price range and in less than optimal position.
I think the key here is to put some real thought into setting your rules and make sure to keep checking on the campaign’s progress, even after automation.