The wording of a dinner party invitation can say a lot about the upcoming event and let the guests know in advance what to expect from their evening. Beyond the necessary data - date, time, place, occasion - the way that you convey this information will let your guests know what sort of occasion to prepare for: a formal sit-down meal, a fun theme party, a casual potluck or barbecue. Show etiquette and formality in the wording and look of the invitations, and your guests will know to expect a formal occasion. But with more casual parties, you have more leeway, as long as you include all the critical information about your event.
Identify the hosts of the party. For more formal events, this is often the opening of the invitation: "Mr. and Mrs. John Smith request the honour of your presence..." or "invite you to join them..." If the party is a benefit or organizational event, the hosts or hosting group might be at the bottom, with the RSVP information. For small casual dinners, you might just include a first name.
Identify the theme or occasion: "graduation dinner," "casino night, with cocktails and small plates," "Halloween buffet + candy" etc. Try playful or clever names for more casual affairs, but stick with classic simplicity for more formal events.
You can write the date and time in a surprisingly large number of different ways. Write everything out for the most formal invitations: "Saturday the fourth of October, two thousand and nine, at half past seven o'clock in the evening." You can announce semi-formal affairs with the straightforward "Saturday, October 4, 2009, 8:30 p.m." And for more casual gatherings, you might abbreviate more or use distinctive punctuation ("Sat 10 . 4 . 09 @ 8 '30") but just be sure that there is no possibility that your guests will misread the date and time of your party.
You may also want to include an end time, especially if many of your guests have children.
Give the name of the party venue ("Seacliff Hotel and Resort," "Le Cirque," "Highland Country Club"), or use something "at the home of Dr. and Mrs. Richard Doe" if it's appropriate. Spell out all words in addresses for formal invitations, and numbers if they aren't too cumbersome: "One thousand Valley Boulevard, Mar Vista, California." Otherwise, write the address as you would on a letter, or if it's a small, intimate gathering for friends, just include the street address.
Write any special requirements for the party near the end of the invitation. You can inform guests of clothing requirements ("black tie only," "semi-formal attire," "dress to impress,"), let them know that they can extend the invitation to friends, ask them to bring food to a potluck, or tell them about the alcoholic beverage situation ("signature cocktails," "wine and beer," "cash bar", etc.).
Finish the invitation with RSVP information, so that guests can let you know if they can attend. A formal affair might have a separate RSVP card enclosed, or may simply print "RSVP" at the bottom of the invitation with appropriate contact information. You can ask your guests to RSVP or "kindly respond" by a certain date. Include your e-mail address or phone number as a way for guests to contact you with their responses or questions.
You can mail an informal dinner party invite as little as 2 weeks before the party. But if the dinner party is formal, mail the invitations 30 days in advance.