How do you chose a research question?
How do you decide what it is that you are going to spend the next 3-7 years of your life on?
You are going to wake up at 3am gnawed by this question. You are going to find good data if you pick a good question. You can construct a great argument if you pick a well-focused question. You can get funding and publications if you ask a relevant question.
Often, people say something like ‘I want to take my time and pick a topic that really fires my imagination‘. That’s a great idea–but what will still fire your imagination when you’re correcting commas in 400 footnotes? what will still fire your imagination when you are up to your thighs in swamp water counting mosquitos? what will still fire your imagination when your experiment has failed yet again?
My usual advice to people at the beginning of a thesis is:
‘Don’t pick something that you love, that excites you. Over 7 years of part-time research you will get bored, you will fall out of love with it, it will become a chore not a passion.
Pick something that annoys you, that makes you angry, that is an injustice. Revenge is a dish that is best served cold, and you will find that you are much more motivated over the long-term!’

It worked for me!