Ask HN: how do you decide which idea to use?

I've got a lot of ideas to try to solve problems and create value for the user. Some are smaller that a two person team can complete, and others that require at least a business person and a finance person and a bigger investment. Right now I'm trying to decide which of these to start, so I'm curious how to decide which to do. The ones with smaller investment / small payoff? large investment / large payoff? the fun projects?

btw, I would love comments on some of my ideas @ lchou1.blogspot.com