Recognizing Problem Buyers

1. Asks alot of questions
There is such a thing as a stupid question and too many questions when it comes to eBay. The stupid questions are the ones that are answered in the listing information:  what size is it, does it have this accessory, is it working, how much is shipping. These buyers tend to send multiple messages. In our experience, these people often don't bid, don't pay, or complain.
2. Wants a favor from you
Offers less than starting auction price on a newly listed item or less than half of listed buy it now price, wants free shipping, asks for item to be donated to their charity, asks you to mark an international package as a gift.
3. Wants to "do you a favor"
These buyers send messages saying things like, "this item is worthless" in its current condition, without missing piece, untested, etc. Yet, as a favor to you, they are willing to buy your "useless" junk at a reduced cost and pay to have it shipped...?There are other "helpful" buyers who want to tell you how to list your items for sale. 

What's a seller to do?
Block them. Don't fret about it, just do it. At weak moments, we've given in and answered their myriad questions and given them price breaks, and it very rarely works to our advantage. Follow your instincts. You know the difference between reasonable and unreasonable. In my former jobs, dealing with unreasonable people was part of the job. Not anymore, suckas!