A good set of question, by Amir Khella, about how to probe a new startup idea:
- Which one excites you the most?
- Which one can you do something about right now?
- Which one can you get feedback about sooner?
- Which one can you get done with the least amount of outside help?
- Which one solves your own pain points?
- Which one aligns the most with your purpose?
- Which one would you like to work on for the next 10 years?
- Which one is likely to remain significant a few years from now?
- Which one do you not mind killing?
Do you really have to choose just one though? Pick several, and apply Hypothesis Driven Development to all of them at the same time, in parallel (a lot of the process is waiting time anyway). Whichever one gets to the point where it takes over your whole day first, is the one that wins.