Wave. I must remember to wave. Take my hand off the steering wheel and wave. Shake my hand in the air as a car drives by the house to wave.
My little guy has this down, especially if you are in a truck! I am sure that I have been seen as rude because I forgot this little cultural thing to do. It is not second nature for me to wave to strangers or passers by.
Back at home, if I did this, I would be stuck with my hand up in the air! The only time I waved was when I actually knew the person.