A good salesman should know his goods. So, before you sell the pencil, study it. Not be amiss to articulate all their actions to the interviewer, for example:"I want to know what I sell. So, this is a simple pencil. It is automatic. On the opposite end of the penciland there is eraser and he's already a little used. And inside there is a container for spare rods".
A good seller should know the needs of the buyer. Usually this information is taken from various studies of public opinion, but you have no such data. So now you need to interview your interviewer, for example:"Now, I want to know your buyer. Can I ask you a few questions? So, imagine that you already have simple pencil. What is it? That may force you to buy another simple pencil instead of your? Whether you value price, manufacturer, shell color, the number of spare rods?"Think of other questions, from my own experience.
A good salesperson must skillfully present your product. The presentation should not be faceless. Now that you know the preferences of your buyer, you can provide him your product. Try to make emphasis on the fact that the interviewer mentioned as important qualities. Feel free to come up with an advertising campaign or a "unique offer" - you're not limited in the choice of means, the problem only to sell a pencil. Sometimes there are problems with coming up with prices. It can be solved, for example, in the following way. At the end of the presentation ask the interviewer: "it is Curious, but at what price would you be willing to buy this pencil now?". As soon as he called any figure, nod: "Good, let's checkout".
It so happens that the interviewer is complicated for you, refuses to answer questions or denies that the goods he needs. Don't push him. Explain to him (as the interviewer, not the buyer) that you understand that there are situations when this product is not need to the buyer. Do you think that in this case to spend time on the presentation – is counterproductive and bad for establishing long-term relationships with this client. Again returning to their role, say, for example, the following:"I can see that this pencil is not interesting. Our store have a lot of useful office supplies. Let me show you some of them." If the interviewer agrees to this option, start all over again with another subject.