Whenever you are with a lady and someone is driving somewhere, you always open the door for her. Try to open the door for her when exiting the vehicle, but it is not always possible as they get out before you get there.
Anywhere it is always polite to open a door for someone else regardless of who it is. When it is a pull door open the door and hold it for others then enter last. When it is a push go through the door and stand aside while holding the door so others can go through.
You are never required to hold open a door for someone, however it is never okay to just let the door slam on someone. Just hold it open enough for them to grab the door themselves rather than letting it slam.
Door etiquette is another aspect of being mindful of others. Opening a door for someone, holding a door open for another behind you, or gesturing someone to pass through first, is simple kindness. Good manners can be seen through one simple act.