People, who don't want to spoil their whole evening by sitting around with their hosts, will ask for a to-go plate for their dessert.
Similarly, it is often expected to carry home a heaping plateful of food for the husband or wife who didn't want to join you for dinner.
I have learned the hard way that if I am going to give someone some food to put it on a paper plate. It seems that if you give someone cake wrapped up on your best china plate, they consider that your plate is a gift to them as well. After more than a month, I had to go ask a neighbor for my plate back!
There is a reason why the custom is that the food is plated and served to guests instead of serving buffet style. At one gathering I had 6 pounds of fajita meat for 12 guests. The first guest put about 3 pounds of meat on his plate.
A friend told me about putting bottles of liquor out for people to help themselves at a party. They did − some uninvited guests carried a quart size bottle of liquor to their table and finished it off. The same thing happened to me with bottles of wine − an uninvited guest and his girlfriend finished off every bottle I opened and then asked me for more. They could barely stand up or talk at the time.
Many people arrive at parties hours late, eat or drink everything in sight and leave immediately.
Guests are routinely two or more hours late to any function, even weddings or a sit-down Thanksgiving dinner. If you are invited for 7 p.m., don't go at 7 p.m. or you will be the only one there for the first hour.
It is not unusual for late wedding guests to make loud entrances while the bride, who has already postponed the actual ceremony for two hours waiting for the guests to arrive, is walking down the aisle.
A party or wedding invitation is assumed to mean that the invitee can bring along everyone from his next door neighbor to their distant cousins from out of town.