Reciprocity and symbiosis are good manners.

When someone makes a gesture toward you in making life easier for you or helping you in some way, pay him or her back.  If they invite you for dinner whether or not you have the dinner with them, call them the next day to thank them.  Never accept an invitation to dinner and show up empty handed. If you cannot think of an appropriate present, a scented candle or music tape is always appreciated, then you must bring a bottle of wine or flowers. If you go to a party, eat the food, drink the wine, meet new people, next time you go out and invite them for dinner pick up the check and send them a thank you card. Pay back and reciprocate.