A good sales person needs to be friendly and professional, to be a good listener and an excellent speaker. Above all they must be confident and extremely knowledgeable about the products they are selling.

Give an example of a time when you had to sell an unpopular idea to someone

If you have an example from work experience this is ideal, however, do not be concerned if you do not. You could give an example from your private life, such as persuading a friend or family member to get involved with something they were not really interested in. Good sales skills are transferable to life.