RESPOND TO ALL INVITATIONS
RSVP means please reply to the invitation. It does NOT mean reply only if you plan to attend. The most frustrating part of hosting, be it a party, a group or another couple, is people who are discourteous enough not to respond, PERIOD. Good etiquette and good social courtesy DEMAND you respond, by either calling or writing to say yes OR no.
NEVER ARRIVE EMPTY HANDED
When you go to someone's home for a party, ask if there is something you can bring. (it's amazing how many supplies, other than food are used up at an average party.) If you are not going as a couple, a house- gift is appropriate (and not necessarily wine.)
CALL TO SAY THANKS
Most people only use the telephone if they are going to go somewhere. Lost seems to the social ambience of a 'Thank You Note' or phone call to someone whose hospitality you enjoyed. It means a lot to most people, and they will surely remember you when planning their next event. Don't you like to be thanked?