You pretty much can judge a book by its cover. Within 1 minute, I know if the salesperson (cars, real estate, consumer durables) is someone that suits me and that I want to earn my commission.
They have to be knowledgeable, somewhat polished and not be pushy.
I sometimes run into people who don't know much. I've had to explain the VVT concept to some salespeople. They didn't even know it was under the hood of the cars they were selling.
If someone comes and starts talking down to me or getting real back-slappy right away, I check out. I'm thinking: act like a sales professional...it's the profession you chose, after all.
I decide when and how much I want to write a check for every month. There are others out there who don't have as much restraint in this area. A salesperson who is going to decide for me has lost the sale. (By the way, the realtor lady who is married to the doctor KEEPS calling me all the way across the US -- thus, she lost a potential sale a LOOOOONNNNNGGG time ago). I absolutely hate lingo like "how'd ya like to driving this off the lot today?" as you barely walk up to a car. What's going through my head is "f*** you."
Basically: A good salesperson knows their product, HELPS you buy what it is you are looking for, can size up who they are dealing with and adjust their performance accordingly.