In our campaign we are looking to expand on the 5th edition backgrounds and personality traits. The world of Planescape is a world centered around belief and we want to start bringing in our PC's beliefs from an early point in the game.
To that end I am composing a list of questions for each PC to answer 2 or 3 in order to provide hooks to develop their beliefs and have characters that believe something from the start.
What is your most cherished/hated memory?
What is the greatest lesson you have learnt thus far?
What did you fear when you are ten?
What is your deepest fear?
What do you want to become?
What do you fear you'll become?
Who/What do you serve and why do you serve them?
Have you ever been in love? With whom? Do you still love them?
If you must die, how do you want to die?
What was her/his name and why do you remember it?
I'm still trying to think up more questions. The idea is to have questions that can be delved into later but still answered fairly quickly. The short answer is both important to get players to actually give one and so that GMs don't have to dig through long complicated PC backstories, the campaign is supposed to be the great thing the PCs do not their backstory. Things that can be referenced quickly in other words.