Trying to lease my first luxury SUV - Help please?

New at this- and want to get the game started. Looking at Mercedes GLC, BMW X3 & Lexus NX. Not fully loaded.

What are the first questions I should ask a dealer? Do you go in asking about residuals and money factors? Am I dreaming if I don’t want to pay more than $400 a month for one of these cars for 3 yrs/ 10k miles?

Thank you for any assistance!