In praise of good manners
Today it's Deroy Murdock's turn (more details in his article),

1) We can hear you now. Even if your party cannot understand your cellular call, those around you often cannot escape your every word. What you ate for lunch and where you are standing right now is far less interesting to them than to you, so restrain your voice. Or better yet, stay off your phone when surrounded by others.
2) Excellent venues to disable cell phones include restaurants, theaters, and funerals, the last four of which I attended were interrupted by mobile phones. Also, there is nothing quite like being in a restroom while a stranger screams his life story into a handheld device.
3) Except for Dionne Warwick, we are not psychic. So, use your car's turn signals.
4) Push in your seat when leaving tables in restaurants, libraries, and conference rooms.
5) Before exiting a bathroom, close the toilet — lid and all. Leaving the lid or seat up makes the next guest contemplate whether you stood or sat during your visit. Spare him or her that imagery.
6) It remains civilized to hold open the door for someone who is walking a few steps behind you.
7) "Please" and "thank you" are not vulgarities. Use them generously, especially around children.
8) "RSVP" means, "Tell those who have invited you to an event whether you will attend." They will welcome your "yes" or regret but appreciate your "no." Not replying leaves them perplexed, unclear of how many guests to anticipate, and miffed if you eventually arrive unexpectedly.
9) Thank you notes, e-mails, and phone calls are appropriate when someone has given you a present, meal, or significant favor. Not even acknowledging a Christmas gift, in contrast, is particularly boorish.
10) Always leave your phone number with your phone messages.
11) Control your kids. It's not cute to let children run amuck on airplanes, kick the backs of people's seats, and holler uncontrollably. Teach your children to restrain themselves in public rather than terrorize grown-ups.
12) Trash cans are there for a reason.

As for item 8, RSVP, I really mean it -- in the last 4 years, every time I've had a party or dinner I've ended up calling a few people at the last moment. Please, do tell your host/hostess if you can make it or not. If you can't make it, you don't even need to come up with an excuse, just saying you can't make it is sufficient with me.