Been selling online through forums (Toyota Supra stuff), facebook market place, craigslist, offerup/letitgo
A couple of items i do on both selling and buying.
As a seller,
1. as-is, where is on items. If electronics i make video time stamped to show condition and if working. Any issues once recieved by buyer must be filed through shipping company ( i always put insurance on packages).
2. Background check to best of my ability, i have caught scammers just by simple searches. Not going to divulge how but lets just say most are a bunch of lazy f's or have zero imagination.
3. Paypal goods and services AND make damn sure tracking info is supplied to both the user and PAYPAL. So far have not lost a case of incorrect shipping.
As a Buyer
1. See #2 above
2. Note red flags like high pressure sales tactic, simple grammatical errors. Unsolicited messages to contact outside of where ever I am at (even craigslist you can communicate successfully without having to IM or text someone).
3. I only use Paypal goods and service and a credit card that has my back. As of this post, have not need to use either and I just recently purchased some high ticket items from within CONUS and Russia.
4. Common sense, if something is to good to be true, more than likely it is!!!