The Wall Street Journal just posted an extended article, actually the product of four interviews, with four start-up coaches. I won't try to echo their advice, just give you the link.
The relevance here, to this site, Selling Face-to-Face, is that a lot of readers of the blog, and of my how to sell guides, are people who are already engaged in, or considering undertaking, new business start-ups. Reinventing your career (voluntarily or involuntarily)? Considering self-employment? Got a new better mousetrap-- or better App-- you think (hope?) the market really, really needs? You'll find some savvy advice in this article.
Link to Wall Street Journal article "4 Low Cost Ways to Guage Demand for your Start-up"