When I lived in Massachussetts I was told never use water on outside ice. Made sense then, makes sense now.

Get in car, turn on all heats/ defrosts/ vents, get out of car so you don't die.

Stay warm by working on what is on outside of car but leave windows/windshields alone for a while. Yes, roof is important.

Do not leave running car alone.

Do not lock keys in running car.

After at least 5 mn, think about getting stuff off windows/windshields.

I have locked my keys in my running car twice. Two different cars, a decade or two apart. Both involved me trying to do a good deed.

My current car won't lock with the fob in it.