My tip would be: treat the interview as you would treat a potential sale, that is exactly what it is. Make sure you are preparred, have all the material you need to present to the business that you already researched on what their needs are and how you can help them. Ask them questions "what is the most important quality you would need a sales rep to have for your company?" and listen. Most of it is asking the right questions, listening and then after they are done talking you tell them how you realize that is important to them and you have that quality they are looking for (my giving an example on your previous work or life experience). If they ask you if you have any questions, ask them something about themselves "how long have you been in your position for?" You just need to prove to them that you are going to be able to make sales and increase their bottom line.