Go through your ideas and pick the one that you yourself need and that you can make at least a version 1 of in a reasonable time. Then do so, preferably with a

Go through your ideas and pick the one that you yourself need and that you can make at least a version 1 of in a reasonable time. Then do so, preferably with a friend you've known for a while and who you admire for his/her ability. This was the recipe for Apple, Microsoft, Google, Yahoo, and many other startups.