You may first want to ask some direct questions to make sure you have all the information you need before giving your recommendation in this scenario. First, you want to be knowledgeable about the product. If the interview gives you an example, saying that sales have been low, that gives you a place to start. Think about how you would measure the effectiveness of their current strategy. Just because sales are low doesn't mean that they are marketing to the wrong demographic. Explain the process you would recommend. Once you have all the data, how would you decide what needs to be different in order to boost sales? What is your experience in this area?