I'm a rather confident and informed buyer. I'll only ask a question or two if specific things are omitted from the ad that I personally want to know/require knowing, or need to know in order to conduct a transaction.
In my ads for local buy and sell I usually state just that,
"Confident and informed buyers only please! No tire kickers, no low balling. Thanks!"
Seems to limit the riff raff and the stuff ends up selling fairly for both parties.