internet scams how to avoid??

As some of you know I'm trying to sell a 64 valiant--i put the ad on a couple of cl locations-- Bam-- instant hits- of I will buy the car site unseen what is your email?
Today i get a text-- have texted back/forth -- seems fishy wants to paypal no other means to pay, I told them to call me & we can discuss..

anyone have a way top weed these scams out -- or is it just the times we live in & if you let your guard down something of yours will be misused.
Anyone have suggestions to limit the scams or is it just beware. & what is it wanting my email address --what are they doing with them? thanks Lawrence