After a ton of research, I determine what I want and how much I want to pay. I then go to the dealer or private party and I tell them what I will pay. That amount you will pay needs to reflect the research you did, your love for the item, and also be reasonable. They say yes or no. It really is that easy. It all starts with the buyer, not the seller. The buyer has to know what they want and what they will pay or the seller is in charge and that never works out for the buyer. IMHO if the buyer budges, then the buyer didn't do the right amount of research or came in with an unreasonable amount based on their research. Keep it simple. Prepare and stick to the plan.
Good luck and have fun with whatever you do buy! :)