Much like my other topic, about "the perfect clients", here's a topic about the perfect sellers.
At some point, you'll end up with sellers you can barely stand to do business with. Either due to bad communication or the feeling of them being unprofessional somehow. - But, you'll often do business with people like this at some point, because you "have to".
What decides and who is the "perfect seller" to deal with?
I would say people that communicates well, (no matter if they're native in English or not). It's important for me to know exactly what I'll get, and it's also equally important to know that the seller understands that I'm looking for.
Other than that, it's nothing truly important except the fact that they should be able to deliver what they promise. - These things are vital and these things will make me want to do business.