How do you know what you know? What's the evidence: Is it credible?
What viewpoint are you hearing, seeing, reading?
Who is the author?
Where is she/he standing?
What are his/her intentions?
How are things connected to each other?
How does `it' fit in?
Where have you heard or seen this before?
What if...? Supposing that...? Can you imagine alternatives?
What difference does it make?