A very funny old movie that is worth seeing.
This little tidbit of social info will seem decidedly anachronistic in our current era of extremely informal backyard barbecues and/or beer and all-you-can-eat buffalo wings, chips, and runny salsa for US$3.99 as you hold up the bar in the local sportsbar and stare mindlessly at the flat-screen TV on the wall without actually looking at the people to whom you are speaking, but it's still worth knowing if you aspire to kick up your everyday style several notches. Sooner, or later, you will be invited to a more formal evening sit-down dinner with tablecloths and place settings. So, you'll naturally want to come across as polished, urbane, and practiced in how you conduct yourself before and during the evening. You don't want to embarrass yourself (or anyone else) after all.
When you are invited to someone's home for the evening, it is polite to bring some kind of tasteful host/hostess gift. That should go without saying. This item might be a small potted plant, a bunch of flowers, a small box of good quality chocolates, or the ubiquitous bottle or two of table wine. You are showing your appreciation for the invitation with things like these. Beyond that, and unless you are asked to do so specifically -- or if the event is one of those (usually. . . but not always) godawful stand-up potluck affairs -- do not under any circumstances confuse the issue by asking "Great! Now, what can I bring?"
Assuming care and forethought have gone into the meal to which you have been invited -- We aren't talking about pizza and beer for the Big Game on TV with your best buds from college! -- there is no need for you to bring the salad, the rolls, the first course, the last course, the dessert, or whatever else might enter your mind in the middle of the night. If you are actually asked to bring something for the meal, great. If, instead, the answer is "No, thank you. We've got it all taken care of," then accept that and stop insisting to the contrary. You might think you are being nice, but the chances are pretty good that your host(s) have put some care into planning the meal, and what you bring might not fit in with that very well with the evening's theme or menu.
Besides that, a spate of nervous last minute telephone calls asking, "Are you sure I can't bring X, Y, or Z?", like the kind we invariably get from the wife of a couple with whom we are good friends whenever we invite them for dinner, is obnoxious in the extreme during the 90 minutes before arrival time as your hosts race through final preparations. That's almost as bad as badgering someone for an invitation. Don't do it! You don't want your hosts to consider striking you from their mental future invitations list after the evening is over and everyone has gone home, right? I didn't think so.
Nope. It really is better when you accept a dinner invitation to purchase the host/hostess gift beforehand and leave it at that. Be a guest for the love of Pete! It might also be a good idea to shower, shave, clip your finger nails, and put on clean clothes before leaving home too. Don't forget to tuck in your shirt and wear a belt either. Remember. You're not having a cold one with your cousin in the backyard after helping him install a new sump pump on a steamy Saturday afternoon in July. A sit-down dinner is a more formal occasion and deserves to be approached as such. Your hosts will appreciate your efforts. Even if they say nothing.