First you'll want to build up an email list of interested customers. That'll be your launch list. In the mean time, you'll want to contact the list to see if t

First you'll want to build up an email list of interested customers. That'll be your launch list. In the mean time, you'll want to contact the list to see if there's anyone who has a burning desire for the product right now. These are your Early Evangelists that will guide your product development. Their need for the solution is so great that they're willing to work with you even from the 'napkin idea' phase. If you're unable to find a handful of these Early Evangelists then either a) you don't have a problem with a big enough pain point or b) you're bad at reaching your target market. In either case you'll want to fix that.