A simple set of questions are defined by Kipling in his immortal poem:
I have six faithful serving men
They taught me all I knew
Their names are What and Where and When
And Why and How and Who
They are also known by the less prosaic '5W1H' and are useful for general questioning and probing. Here are some question 'starters for ten'...
Where are you?
When, exactly, will you...?
When will it start/end?
When will I know?
Why does that happen?
(just keep asking 'why?' to find root cause - often around 5 times)
How does it work?
Who will do this?
Who else will do this?
WHO, WHAT, WHERE, WHEN, WHY HOW?