This is a great (the only?) way to start. One thing I think is also really important is to be a domain expert in the field of your idea, or be ready to find co-founders who are.

Obviously domain expertise isn't totally applicable for something like having a great idea for a new spin on a social network, but where you are getting into a vertical (like healthcare) it is probably essential. Otherwise you won't know how to make a product that the professionals in that market truly want.