You're idea about counteroffering what "you" perceive to be low-ballers is an excellent idea. I once made an offer of $650 on an $850 item. I was willing to go to $750, which I thought a fair market price. The seller (a regular seller) never responded. Two months later he lowered the price to $750 and it was still sitting there for a while after that. Meanwhile I had moved on and bought it elsewhere for $725.
I'll add something to your list - don't be curt in your correspondence. I asked a seller one simple question. The tone of the reply was "don't bother me with questions, just buy the damn thing". I always avoid buying from someone with that attitude because if they're a problem before you buy it, chances are they'll be a problem if something goes wrong with the transaction. I moved on.
A third problem I had, which is actually similar to the "curt" problem I mentioned above, was after bidding and attempting to make a payment I got a return email saying the payment didn't go through because the seller's account had a problem. I informed the seller (I believe he's a business because he sells a lot) about the email and the reason stated. He basically said pay up or else. After some digging I found out something had gone wrong with the Audiogon-to-PayPal connection. I reconfigured it and sent the payment again and it worked. But due to his attitude I'll never buy anything from him again. And in fact, there have been several instances where I've come across an item, saw it was him, and moved on. So the lesson is, don't assume someone is jerking your chain. There may be a legitimate problem.
I'll add something to your list - don't be curt in your correspondence. I asked a seller one simple question. The tone of the reply was "don't bother me with questions, just buy the damn thing". I always avoid buying from someone with that attitude because if they're a problem before you buy it, chances are they'll be a problem if something goes wrong with the transaction. I moved on.
A third problem I had, which is actually similar to the "curt" problem I mentioned above, was after bidding and attempting to make a payment I got a return email saying the payment didn't go through because the seller's account had a problem. I informed the seller (I believe he's a business because he sells a lot) about the email and the reason stated. He basically said pay up or else. After some digging I found out something had gone wrong with the Audiogon-to-PayPal connection. I reconfigured it and sent the payment again and it worked. But due to his attitude I'll never buy anything from him again. And in fact, there have been several instances where I've come across an item, saw it was him, and moved on. So the lesson is, don't assume someone is jerking your chain. There may be a legitimate problem.