Dear Etiquetteer: What is the proper etiquette for what to bring to a dinner party? Does one always simply ask what to bring or perhaps just a nice bottle of wine? Does one ask what one can bring if it is not mentioned in the invitation?
Call Etiquetteer old-fashioned, but Etiquetteer prefers to maintain that a Lovely Note of Thanks after a dinner party is much more essential, and Perfectly Proper, than a hostess gift. That said, flowers are the safest choice for a gift, with wine running a close second. Etiquetteer ranks them in this order because the number of people who are allergic to flowers is less than the number of people who don't drink wine.
As you point out, sometimes hosts will specify what they would like to guests to bring; honor that as closely as possible. If hosts don't include a preference in their invitation, by all means ask if you're so inclined. But be warned: you might get more of an assignment than you bargained for. Etiquetteer vividly remembers asking one hostess "What may I bring?" to be given the reply "Oh, the dessert!" This was more work than Etiquetteer wanted to do, but having asked in the first place, Etiquetteer gritted his teeth and baked a cake. Etiquetteer still thinks of this as a bait-and-switch invitation; having been invited to a dinner party, it actually turned out to be a potluck.
Hosts should also be prepared for this question, and Etiquetteer encourages general instructions rather than specifics, e.g. "Oh, just a bottle of red you like that will go with roast" rather than "a couple bottles of Chateau de la Tour de Bleah 2008." This gives the guests the opportunity to stay within whatever budget they have.
But Etiquetteer really thinks the best response to that query is "Please bring a smile and a couple good stories!" A dinner guests "sings for his supper" best with a contribution not of a bottle, but of one's camaraderie and good humor.