Kiss those casual summer get-togethers goodbye. Washington is back to the full-time business of networking, schmoozing and fund-raising. Hostesses start drawing up lists for elegant little sit-down dinners. Campaign managers draw up lists for massive meet-and-greet fund-raisers. Charity balls, tailgate parties, school bazaars, opening nights . . . the celebrations go on and on.

There are so many invitations to so many events that a good invitation is crucial. The truly great invitation sets the tone and creates instant interest: One minute it's an envelope in the mailbox, the next an eagerly anticipated date on the calendar.

Several years ago, the Folger Shakespeare Library sent a gorgeous invitation for its annual gala to Maggie Wimsatt. She doesn't remember the details, just the feeling she got when she opened the envelope. "It was so beautiful you just knew it was going to be a special evening," she says.

Wimsatt probably sees more invitations than any woman in Washington: After decades on the social scene, she is now considered the unofficial clearinghouse for charity events in Washington.

The days of the handwritten formal note are long gone. Today, most people use store-bought invitations. It's acceptable to telephone, e-mail or fax a guest for informal last-minute affairs or casual dinners, but not for serious entertaining. Washington is an old-fashioned town, and people still like to receive invites in the mail.

"For a formal dinner, there's nothing like an engraved invitation," Wimsatt says. A thick, gold-trimmed card from the White House, for example, confers elegance and class regardless of the event. And this year's invitation for the Washington Opera Ball was a lush piece of artwork trimmed with a silk tassel.

Invitations can be playful and unusual--printed balloons, champagne glasses, videotapes--but excessive cuteness or humor does not, as a rule, play well. And forget about including those tiny, sparkly pieces of confetti inside the envelope. "The invitations that really turn me off are the ones with all the little things that fall out and you have to vacuum the rug," Wimsatt says.

The trick is to convince the invitee that his or her presence is vital to the success of the party. The more personal the invitation, the more a guest feels obligated to attend. A handwritten card is more personal than a printed one, a hand-addressed envelope more enticing than a computer-generated label.

People are more likely to accept an invitation to a small party than a big one where they feel they won't be missed; clever hosts send handwritten invitations for large affairs, even cocktail parties, so every guest feels special.

Grover Norquist, president of Americans for Tax Reform, a conservative activist and relentlessly cheerful host, gives parties at his Capitol Hill town house about once a month. The smaller receptions have 40 guests, the larger up to 100. He also hosts six sit-down fund-raising dinners a year.

Two weeks ago, he threw a party just for fun. He sent printed cards a month in advance and followed up with phone calls to new names on the guest list. "I call, particularly if they're invited for the first time, so they know it's not a pro forma invite."

The standard rules for advance notice suggest that wedding invitations be mailed six to eight weeks before the big day, charity balls four to six weeks, formal dinners three to four weeks, and nothing sent less than two weeks in advance. A telephone invitation, on the other hand, should be closer to the day of the event.

Washington's huge charity balls require a complex early-warning system for inviting guests.

The 14th annual Lombardi Gala, a benefit for Georgetown University's Lombardi Cancer Center, will be held Oct. 30. To get more than 1,000 guests to the elegant black-tie event requires three mailings, says Bonnie Roberts, director of donor relations and events.

The first, an "advance notice card," was sent in February to get on people's calendars. "That's because people start to make their plans early in the year," she says. "It saves phone calls." The second mailing was a "Save the Date" card, sent in June before the vacation season, and included names of the honorees, the theme and information about the gala's live auction.

The actual invitations--5,000 of them--will be mailed Sept. 16, six weeks before the gala. "You try to do it right after Labor Day because that's when people are back and business is back to normal," Roberts says.

It goes without saying that any invitation needs to include the date (double-check both the day of the week and the date--you'd be surprised how many invitations get one or both wrong), the address of the party, and a phone number or address to RSVP.

Specifying a dress code--black tie, business, casual--is not mandatory, but people will call if you don't provide that information on the invitation. "I do include it because it's the one thing people in Washington get very concerned about," Norquist says.

Last but not least, check postage costs. Too many horrified hostesses have bemoaned the lack of response from their guests only to receive the invitations back days later marked "Insufficient Postage." An elaborate, oversize confection may require more than usual. Anything over 55 cents--the cost of mailing a standard wedding invitation--is considered excessive by veterans on the charity social circuit.

"Sometimes people think that if a nonprofit organization spends too much on postage, that they don't really need support," Roberts says. "The challenge is to make a really nice invitation, but keep it within that 55-cent limit."

Actually, the real challenge is getting people to RSVP, but that's a headache for another day.

Roxanne Roberts can be reached by e-mail at robertsr@washpost.com.

CAPTION: Party time: Invitations from Grover Norquist, the Washington Opera and the White House run the gamut from no-nonsense to tasseled.