Who is actually doing the work? Some contractors self-perform, some subcontract everything, and both can work. What you need to know is which one you are hiring, because it determines who is standing in your house and who is accountable when something needs correcting.
Can I see an itemized estimate? A lump sum hides the soft spots. Line items let you compare bids honestly, see where a cheaper material saves real money, and understand what is an allowance rather than a fixed price.
What is the schedule, and what happens when it slips? Every project hits something. A good contractor gives you a start date, a finish date, and a communication rhythm. A better one tells you upfront which parts of the schedule are most likely to move and why.
How are changes priced? The answer should be: in writing, before the work happens. Change orders agreed verbally mid-project are the single most common source of a final invoice that shocks people.
What are the payment stages? Deposits are normal; a large payment demanded before any material arrives is not. Ask what triggers each stage, and make sure the final payment comes after the walkthrough rather than before it.
Who do I call while the job is running? You want a name, not a company number. On a project of any size there should be one person who knows what happened yesterday and what is happening tomorrow.
Can I see recent work nearby? Not a curated portfolio from five years ago — something finished recently, ideally something similar in scope. Then trust the pattern you observe: contractors who are organised during the estimate are usually organised on the job site, and the reverse holds just as reliably.