Ps and Qs...
My Mum and Dad were always big on Ps and Qs. When we asked for anything they'd always say, "What do you say?" to which the only acceptable answer was, "Please". After the thing was given the ineviatably question was, "Now, what do you say?" to which the only answer could be, "Thank you". Please and Thank You. Please and Thank You. Please and Thank You. It was instilled into us from an early age.
Saying thank you works both ways, of course. Not only does the person you're saying it to feel appreciated but also it means that you are the kind of person who actually cares how other people feel. You want some else to feel better. It's a win-win situation.
So I was especially pleased to get an e-mail from Michael saying, "Just a line to say that I enjoyed myself enormously on Saturday night and I hope you did too. Thanks for organising it!"