I'm studying Steve Blank's Four Steps to the Epiphany with an intensity that I haven't mustered for any book in years. I'm talking liberal use of yellow highlighter markers and scribbled notes in the margins. It's gold, I tell ya! I love Steve's advice about uncovering a market that matches your original product vision:
This rigor of no new features until you've exhausted the search of a market space - counters a natural tendency of people who talk to customers – you tend to collect a list of features that if added, will get one additional customer to buy. Soon you have a ten page feature list just to sell ten customers. The goal is to have a single paragraph feature list that can sell to thousands of customers.
The quote is from a passage talking about the second synchronization meeting between the customer development team and the product development team. Roughly speaking, in software anyway, that divide is between Sales/Marketing/Product Management and the Designers/Developers. In a 2-person startup, one founder will probably focus mostly on customer development and the other on product.
You arrive at a true Minimum Viable Product (MVP) after the product development team has already started working on the original vision and customer development team has "left the building" to validate its assumptions by talking to real prospective clients. The feedback from clients is used to trim features from the current product feature list, but NOT to add features. You don't add features until you've become convinced that you're building the completely wrong product - at that point you're probably going to scrap the idea and start over.
This valuable book came out in 2007 and I can't believe that it took me this long to study it! If you are in any way involved in startup activities and haven't bought this book yet you should absolutely get it as soon as possible: Buy the book from Amazon (or if you're not convinced yet then download the first three chapters as a PDF for free from Stanford first.)