Comment by ianamartin

I'm acutely aware of this, and my pattern for phrasing things when I'm new to a scenario I'm trying to help out with is:

"What happens when you try x?"

What very often comes next is a clear explanation of why this obvious solution won't work, and often directs you right to the heart of the problem.

Every once in a while, you get an "Oh. I didn't think of that."

It's respectful, it assumes that person is smart and competent, and usually gets you where you need to go to start thinking about the hard problem at hand quickly.