On top of nostrademons advice, find people who you (and they) can work along with. They will be your family and so you better get along with them well or else perish. If you are building a technology based company, you should be very clear to your cofounder(s) (hopefully some smart technical ones) about what you can bring to the table.
Honestly, talk about your idea and see if people really care about it enough.
Of course, I've also seen this - some really smart business folks writing long business plans and then tell me, "This is our product X [a web based solution often times] that we're trying to build, there's a need for it, etc... Oh, and we just need a website - we could maybe use a part time web developer?" Of course, there is nothing wrong with not knowing where to start, but it's really good to test your assumptions from the get go.
And it doesn't hurt to have advisors - as in people who have done this kind of stuff before. You'd be amazed how much people can share over a piece of pastry and coffee :-)