First and paramount, I prefer to talk to a salesperson with good product knowledge. At the minimum, he or she should know as much as me. Even better if he or she knows more than I do. That way, I can learn something from the chat.
Secondly, I would want someone who is able to negotiate a reasonable discount with me. I understand that everyone needs to make their profit. At the very least, I expect the same discount percentage as other shops/boutiques. I have come across some sales assistant who are stuck up with the if you can afford it, you will buy regardless of the price.
Thirdly, it happens that stock runs out, system is down etc. So if you promise to return call to me, please do so. I will appreciate it.