I've also played with a few Craigslist scammers. They tend to use canned responses to get you to email them back, such as "is it still available?" Isn't that why its still listed? :S
But I also routinely check email headers for IP addresses. If they're from out of town, have had a fair share from Nigeria, I don't usually waste time responding. However, have messed around with a few of them. Such as when they asked for full contact info to FedEx a bank check, I attach a link to a Word or PDF file. No obvious clues as it being anything else. But when they click the link, it re-directs to a local FBI or Interpol office. There's your contact info? Overnight your check there? Even had one scammer get upset, and call me an idiot. :B