What characterizes a good salesperson, according to you? What makes you think that? Which of those traits do you have?
Could you comment on a proposal you once made that was not accepted by your superior? Why was it not? What would you do differently next time?
Could you comment on a proposal you once made that was accepted by your superior? What did you do right this time? Would you do it differently next time anyway?
Could you give an example of a difficult sales interview you have had recently? What was the situation and what did you do exactly?
When was the last time you had to convince someone? What exactly did you do?