Essential to a marketing plan is the knowledge of the target audience. An interior decorating business most likely targets females with an interest in home décor. Based on the style and types of products you offer, the target age and income level may vary. Based on the area where you are operating the interior design business, conduct demographic research to determine what the breakdown of the population in the area is. For example, if there is a high concentration of corporations operating in the area, targeting business clients may be your focus over residential homes. Choosing a target market helps you identify with your audience and then craft marketing messages, services and products that attract and land the clients you are seeking.