Ask HN: Best Market Research method for ideas?

There are a number of methods out there that are used to conduct market research on ideas before any code has been written.

Here are the methods I have found: 1. Sales Safari by Amy Hoy 2. Market Map by Pat Flynn 3. Ad Words from Start Small Stay Small Book 4. Customer Development interviews from the Running Lean book 5. Traditional SEO analysis, from many of the affiliate forums like BHW.

What method do you use to investigate the potential for an idea before you start creating it or writing any code, and how has this method worked for you?