Some scams can be quickly spotted if you think objectively. Take for instance an ad for a $10 wheelbarrow. A realistic reply might be "Still available? Tire hold air? Not rusted out? When can I see it?". A scam reply might be " I am a highle successful international business man, and very busy. I will arrange to have one of my assistants make arrangements for payment and shipment of your wheelbarrow." If it sounds dicey, at least question it in your mind. You don't have an obligation to respond to possible scammers in these cases. Most likely, though, responders to a wheelbarrow ad will be folks who actually need a wheelbarrow.