1. Always deal in cash.
2. Buy/Sell face to face, no shipping.
3. If you are concerned of strangers knowing where you live you should agree to meet at a public place. Maybe a gas station, parking lot etc.
4. Communicate with the seller/buyer via the messaging system on the site. This is the big one that will help you more than anything. The scammers are going to do whatever they can in order to get you to talk to them via e-mail. We recommend you don't do this, period. There is a reason why they want to move the conversation to e-mail... so they can tell you a long story about the product. They know that we cannot filter out the scammers via e-mail as efficiently as we can with the messaging system.
5. If it is too good to be true.... IT IS!
If you run across a scam please use the "Report As Bad/Scam" links throughout the site. If you have experienced other scam tactics we always want to hear about it. Send us an e-mail, tweet about it etc..
As always, if you have questions let us know. firstname.lastname@example.org. Justin McClung