- Cover yourself in your item descriptions. Always state both the condition of your item and the entirety of your return policy very clearly and adamantly in your item listing. If you will accept returns or exchanges on the item, state also the limits of your return or exchange policy, including time limits, restocking fees, and shipment responsibilities/refunds. For AS-IS items, clearly state "This item is sold AS-IS, with no warranty expressed or implied, no refunds or exchanges will be granted for any reason whatsoever; BUYER BEWARE!"
- Block difficult or problem buyers from your auctions. Use the tools on the eBay website to cancel bids from or block buyers with whom you've had problems in the past so that they are not able to bid on your auctions any longer. If you have blocked a bidder and suspect that they have come back under a new user ID to bid again, contact eBay and report it. They will likely be suspended as a result.
- Keep proof of shipment and delivery on hand. When a buyer opens a dispute with eBay or a credit card company, your best defense as a seller is to keep a copy of all shipping information on hand, including delivery date as certified by the shipper. Often such documentation alone is enough to decide a case in the seller's favor. As an aside, if as a seller you aren't using trackable shipping methods for your auctions, consider starting now.
- Report bad buyers immediately. In the cases of auction tampering and payment fraud, notify eBay immediately. Not only does eBay take the threat of fraud and site tampering very seriously, they will also take steps to ensure that such members are banned from the site and (whenever eBay is aware of them) kept out.
- Take payment fraud prevention measures. Both PayPal and most financial institutions hosting merchant accounts have clearly stated policies about the relationships between accepted payments and account information for those payments (including names, shipping addresses, and other information). Read the seller account information provided by your payment processor for details on accepting payments and making shipments in ways that ensure minimal risk to you.
- Protect yourself from bad payments. Avoid accepting personal checks, money orders, and other forms of "paper" payment unless you are willing to accept the risk that they inevitably present. If you accept PayPal payments, connect your PayPal account to a bank account dedicated specifically to your eBay activity, and empty it of funds regularly to ensure that no buyer can initiate a large chargeback or fraudulent claim and freeze an unduly large portion of your assets.
There's No Perfect Protection
Even after taking steps to combat buyer fraud, there is nothing you can do to avoid it entirely, nor will you ever be able to prevent angry emails from buyers who are unhappy, whether you feel that their reasons are sound or not. There also little that you can do to avoid negative feedback that you feel is unwarranted from angry buyers. eBay considers feedback to be an open forum in which members are free to speak their minds about one another, including about any disputes or disagreements that they've had.
Ultimately, if you are a busy seller dedicated to good service, your positive feedback and positive sales revenue will always far outweigh any unwarranted negative feedback or the occasional (and inevitable) problem or fraudulent buyer. At the same time, problem buyers often quickly accumulate negatives from unhappy sellers and are quickly removed from eBay as a result.