It depends on which car you drive. If you're talking about cars like Hyundai that should be easy. Take a long stick or wire and stuff it down the gap where the window is scrolled down to and repeat the up and down motion several times it should trigger the lock to open. But if your car has a activated alarm, it will go off loudly.
I Hope it help, I read this in one of the book that I have, it teaches people who to unlock certain stuff.