You don't spit into the wind.
You don't pull the mask off the ol' Lone Ranger
And you dont stand directly in front of the elevator door when that little light goes off, thereby preventing the passengers of the evelator from being able to leave the car. You especially don't continue to stand there as people are trying to get by you. And if you even THINK about trying to enter the elevator while the people are trying to exit, then don't act surprised when people knock into you, ya danged moron.
The same goes for people waiting for subways and trains too.