I haven't changed much in the manners department since I was about thirteen. Basically, every person I meet starts out with the exact same amount of respect. Their actions immediately following my introduction to them raises or lowers the amount of respect I have for them, and this influences the way I behave towards them.

I have common courtesy when it comes to opening doors. If I'm there first, I open the door and let everyone else go in. I hold the door for people leaving behind me. I don't drape my coat over puddles, because they're fun to splash.