In thinking about starting a business, the single most important question to answer is, "who will my customers be?" Nothing else is as important, as pivotal to financial success, or as defining for your new company. You need to define potential customers as clearly and narrowly as possible.
Narrow is good. Here's why.
The most common impulse is to think -- "gosh my new business should serve everyone -- all 307 million in the US -- why not all 6.7 billion worldwide. If all 6.7 billion people will spend just one cent per day with me, I'll be rich."
The problem is that no business can address 6.7 billion people. What one product or service could you create, market, distribute and support that might be bought by both a Bill Gates and a native fisherman in the Andaman Sea?
The initial customer set that you define needs to be very, very small and very addressable. The customer set needs to have similar unmet needs. Ideally, these customers would be in a small universe that could be a natural reference group for your business. This small group could become your launch customers.
The next obvious question is, "how do I find this small group of potential customers with similar needs?"