One of my favourite practices coming out of marketing is developing customer personas. A customer persona is a detailed profile of your company's ideal customer, or more likely several personas of each different type of customer you want to sell to. These don't have to be dry, dull exercises, you want to convey the personality of the customer you're imaging so give the persona a name and bring it to life.
Customer personas aren't just for the marketing department though. Try looking at the product road-map from each persona's view-point - what will they think of those new features? How about your customer service options, product packaging or returns policy, what will each persona think of those? Used properly personas can give powerful insight into what your customers really value or what they wish you did differently.
Customer personas are also really helpful for investors. A well developed set of customer personas sets the context for the market positioning and can bring the product to life. This can really help give investors confidence that you really understand who your customers are, how to find them and that you'll be able to convert targets to customers.
Developing a deep knowledge of your ideal customer, a concept known in the marketing realm as buyer persona profiling, is critical to increasing the relevance of your efforts.