Dear Etiquetteer: What's you best advice for introverts at parties?
First of all, don't stay away from the party! This is doubly true when your host is a close friend or relative, who may well understand that large gatherings make you uncomfortable at times. If the invitation is for something small, like a dinner party for eight people, the degree of comfort might be greater.
Before the party, there are a couple things you can do to make yourself feel more prepared. Usually it isn't Perfectly Proper to ask who the other guests are going to be; this is because the pleasure of the host's company is supposed to be a sufficient reason to accept the invitation. But under these circumstances, Etiquetteer will allow you to ask, at the time you accept the invitation, if mutual friends will also be there. Knowing that there will be at least one or two people there that you already know can help a lot.
You may also catch up on the news of the day before the party by reading that day's newspaper or one of the news websites. This will give you a knowledge base to contribute to the conversation. If you and the hosts share a common interest, it's likely that others at the party will, too.
If you're really feeling anxious, ask how you can help. Passing hors d'oeuvres, for instance, still requires you to move throughout the room, but doesn't really require a lot of small talk. But even helping to gather dirty glasses or discarded paper napkins gives you something to do and helps out the host. But do ask first; hosts can be fussy about how they like things done.
For large parties, roaming does help relieve the pressure of introversion. Tour the public rooms of the house. Etiquetteer, who occasionally suffers spasms of Party Overwhelm, particularly enjoys being entertained by friends who have a library to which retreat is possible during open houses. This is such a relief when the well of small talk has run dry, or when it just isn't possible to stand up one more moment.
Do NOT bring a good book or spend all night on your smartphone texting (or pretending to text) people who aren't there. That's insulting to the host.
Finally, another introvert might also be there who needs reassurance that they aren't the Only Introvert at the Ball. Here you have a common bond for conversation!
Now go forth and party, and be sure to send a Lovely Note the next day.