I'm not an impulsive shopper. When I'm purchasing a gun, I've done my research, know exactly what I'm looking for and I know what they are selling for used, new, on gunbroker, in stores and at gunshows. Lately, most of the guns I've purchased are either from gun shows or over the internet. I've never been burned on any of my acquisitions - got exactly what I thought I was getting.
If I am looking for a particular gun at a gunshow, I basically put the blinders on and look at/for nothing else. Am I passing up "good deals"? Possibly, but it's not really a "good deal" if it's not somehting I've decided that I really want - so let the next guy find his "good deal". If I find the gun, I ASK to look at it. My next quesiton will be about the price. If the price is better than what I expected from doing my research, I will ask to dissasemble the gun and look at it closer, indicating that I will purchase it if everything looks "right".
If the price is out of the ball park too high, I gently put the gun down and thank the gentleman for letting me look at it. Sometimes the seller really wants to sell it anyway and will ask for an offer. I'll tell the seller that I like the gun, that I know what these guns sell for and tell him my price, which will be what I feel is a fair price, not a ridiculous low-ball. Sometimes the seller genuinely has too much money into a particular gun, other times we strike a deal. Just depends.
If the price is close to what I think should be a fair price, I will throw out what I'd be willing to pay for it - usually the price that I see them selling for on Gunbroker and other forum boards. If I save shipping and the transfer hassle, it's worth it for me to just pay cash and buy it right there.
That's just how I buy guns - it's not rocket science, most people know what the "fair" selling price is for their guns, and as long as you are just trying to pay a fair price for it, you'll probably get the deal you want.