Never ask a lawyer if it's OK to do something (it's always "no"). Ask them to explain the risks in doing so.

Never ask a programmer if something is possible (it's always "yes"). Ask them to explain what is involved doing something.

Never ask a doctor if something will make you better (it's always "maybe"). Ask them to explain the conditions under which a treatment/procedure will work and what could go wrong.

@davetron5000
In all three cases, I'm a big fan of β€œIf I were your daughter/mother/favorite aunt, what advice would you give me?” Their answer usually stimulates the right follow-up questions.

I likewise ask contractors, "What would you do if this were your house?”

@kims @davetron5000 Ah, that last one. Some tiles came off the roof of a rental property in a storm. Should we replace the tiles (cheap), or have the whole roof replaced (better, but not so cheap)?

One of the co-owners asked me "what would you do if you lived there?", so we replaced the roof.