Elevator- when exiting and there is someone waiting to get on- does one exit first and then let them on- or does one let them on and then exit?

Bus- if standing at a bus stop for a long while (and you are the first one there)- do you get on the bus first- have a right to do so?

Superstore self check-out- WTF? What's the proper way to form the line? Who has right of way? Seems like people make up their own rules... —What, me... stupid?