Know what you are buying. Before making an offer to a seller, ask questions to learn more about what they are selling. 

DO NOT do business with anyone offering to send you payment for a higher amount than your selling price, especially if they are buying the item sight-unseen.

Be suspicious of anyone claiming to be acting on behalf of a “client” or another “customer”.

Be suspicious of anyone offering an item for free or at a reduced price, and asking for the shipping fees to be sent to them in advance.

Ask for personal contact information. Once you have negotiated the price and have decided to buy or sell the item, ask for a phone number and call him/her up at a random time to make sure he/she is receiving the calls.

Use a payment method with fraud protection. Many scammers only accept money by wire transfer, Money Gram, or bank transfer because buyers cannot get their money back and sellers cannot be tracked.

Don’t ship an item to a buyer until you have payment in hand, in the equivalent of cash, for the agreed upon sale price.  Avoid complicated payment schemes that involve multiple steps or buyers.

Keep records of all correspondence.  Hold on to any e-mail, notes, shipping documents, and payment information.  Be sure to print a copy of the ad!  These records may prove useful in the rare event that you need to seek a refund from a seller or report an incident of fraud.