Since you're posting this question on HN, I'm going to assume you are trying to do an internet startup.
Are you a hacker or a hustler?
Quick general definitions:
Hacker is the technologist who understands how to use technology to solve business problems.
Hustler is the sales/marketing person who understand the specific market vertical (customer problems) and has the ability to sell whatever the hacker builds in that market.
If you're a hacker, finding hustler co-founders is pretty easy. Look for a subject matter expert (SME) in the market vertical you are going after. They should be able to give you all the info you need to penetrate that market (customer pains, sales strategies, introductions, price points, etc). Al they have to do is tell you what to build, then sell it.
If you're a hustler looking for a hacker, it's much more difficult. Any hacker that's actually capable of playing an integral role in your success is already working on another project. The only place I know of where you can find decent talent is in corporate America. Find the person living the office space movie and offer them a path to freedom.
If you're a hustler looking for a hacker, you have to be one hell of a hustler to get any respect. You have to nail down every possible non-technical aspect of the opportunity. And it better be one hell of a good plan you put together. It has to be so well put together that the hacker knows immediately you are the real deal and all the hacker has to do is hack.
Being a hacker who's been approached by a lot of hustlers over the years, let's just say you have your work cut out for you (assuming you're the hustler looking for a hacker).