[wdfifteen]

My policy is that I take the inquiries in order. When I get 4 or 5 I take down the ad. I get a time certain for the exchange from the first respondent and send an email to the other's letting them know where they stand in line and when/if the 1st respondent closes the deal.
With the internet, communication is easy, why not use it.

I guess you could say I hold it for the first guy, but if the first guy won't give me a time that he will close the deal I assume he isn't interested and move on.

I've sold quite a bit of smallish (under $1k) stuff on Craig's list in the last few years and only had a couple of hiccups. Once the first guy missed the deadline and I sold it to the next guy in line. The first guy whined and moaned and gave me his excuses for not making the deadline. I told him the excuses might have done some good if he had let me know BEFORE the deadline. With texts, emails, and phone communication available there is no excuse for not communicating.
The other problem buyer kept extending the deadline to close the deal - like 3 or 4 times. I finally gave him a final deadline and he said he'd have to pass. By then buyer #2 was no longer interested.