Silicon Valley has been buzzing recently with the news that Facebook bought Instagram for $1B. I always caution against taking too much away from these outlier success cases. In science, that's known as sampling on the dependent variable. However, they make some good points about making sure that you're passionate about the area of your startup idea, such that it is related to a theme in your life and something you're willing to be constantly thinking about and developing.
Here are the Instagram founders, who are Stanford alums and former Mayfield Fellows Program students talking about when the "idea" for Instagram came to them. They share a lot of important insights. Be sure to check out the rest of their talk as well.
A recent NYTimes article is here.