Your customers most likely all bought your product or hired you because you fixed an issue they were having.
(Yes, some businesses cause something new to be built or a goal to be achieved, but most sales are made because the buyer needs something to be made better, now.)
Thus the two business critical questions are What is the problem you solve? And  Who exactly has this problem?
The answers to these 2 questions are the fundamental parameters of your niche markets. Your very best top quality prospect is a person who has the problem you can solve.
Who are these people and how can you find them are the cornerstones to the concept of prospecting.
Before you launch your business or a new product, spend some time on these two questions. Because sales are much more easily made when speaking to people who have the problem you can solve.