SUMMER is here and so are the tourists -- in your house.

Believe it or not, your guests are not staying long enough to see everything--and you can be perfectly charming if you get your own way. Just take them to your favorite places.

The simplest attractions, even the most jaded Washingtonian will admit, remain perpetually fascinating. Here are some ideas for those of you who have seen every monument a thousand times, but are still determined to do your bit for your eager tourists.

Hope Diamond--Filed under Gems and Minerals in the Museum of Natural History. You won't read on any plaque that the Hope Diamond has been tainted with bad luck (financial ruin, illness, death) for many who have owned or touched it, or that since Harry Winston gave the 45.5 carat rock to the Smithsonian, the United States has been in war, recession and so forth. But it's fun to regale visitors with such tidbits. There's also a glowing display of phosphorescent samples, where your guests can pick out the ones from New Jersey.

Insect Zoo--Also in the Museum of Natural History. Tarantula feedings three times a day around lunchtime. The hospitable docents are keen--if you are so inclined--on letting you touch most things. In this hall of morbid fascination, you might think the glass on one cage is in need of Windex until you discover on closer inspection that it is plastered with baby walking sticks. Another mesmerizing game for both children and adults: searching for the queen in the live beehive.

Foucault Pendulum--Another favorite because it moves. View it from the Constitution Avenue level of the National Museum of American History so you can be part of the cheering crowd when the pendulum knocks down one of those little pegs.

First Ladies' Gowns--Your ticket--in the same museum--to avoiding the long lines of the White House tour. The mannequins are in rooms that are reasonable facsimiles of the Red Room, the Blue Room and so on. You can also look for Dorothy's ruby slippers, Tai and Randy's skating outfits and the Supremes' dresses.

Air & Space Museum--If you're a regular, you'll be cheered to hear there's a new exhibit hall, "Stars," that will indeed make you feel small. You can even check what your sign of the zodiac will look like in 100,000 years. An old favorite, a short film called "Powers of 10," has been relocated at the hall's entrance.

Snapshots--Step outside and take pictures with the Washington Monument in the background. Or for some memorable group shots, the Hirshhorn Sculpture Garden statues provide amusing extras.

Whispering Gallery--The Capitol's Statuary Hall--the old, semi-circular, vaulted-ceiling chamber of the House of Representatives--just happens to have all the right (or wrong) architectural dimensions. The room carries a whisper from one side to the other. Legend has it that John Quincy Adams tuned in to the opposition's strategy while pretending to sleep at his desk. But acoustics have it that the opposition had an equal advantage.

The Municipal Wharf--You can point out the Jefferson Memorial en route to purchase the local dish. For some reason, the blue crab isn't recognized in its shell by people north or west of Maryland, so one feels inclined to introduce them to it.

Lincoln Memorial--Worth a stop even though your guests will probably be disappointed that they can't crawl up in Mr. Lincoln's lap to have their pictures taken.

Vietnam Memorial--Just filing past the 57,939 names is immensely moving.

Einstein Statue--In the park across the street. Visitors allowed in the genius' ample lap.

Short Drives--Past the Kennedy Center ("the box the Watergate came in," as one wag calls it) and Howard Johnson's Motor Lodge ("the inn the Democrats were bugged from"). Head into Georgetown on the old Whitehurst Freeway, gaze across the Potomac at the skyscrapers now accepted as Rosslyn and remark wistfully, "20 years ago, Rosslyn was an Italian restaurant with plastic grapes hanging from the ceiling." Don't forget Georgetown Park ("something out of M.C. Escher").

C&O Canal--Another landmark they're not likely to match back home. Repeat visitors--and hosts--who have done the monuments enjoy renting bikes at Fletcher's Boat House and pedaling a few of the 184 1/2 miles from Georgetown to Cumberland. For lunch you can stop at Market House in Georgetown, where one of you can stand outside with the bikes while the others go in for the hot dogs. You could also take your throng on a mule-driven barge trip. Although touristy, the roof-covered barges--departing Georgetown and Great Falls, Md.--keep you moving in the rain.

Teen-agers--Because they are apt to be harder to please, try first assuaging their curiosity for the pandas at the National Zoo and then send them off to the Metro stop several blocks south. For 75 cents each, they'll go happily underground for hours on the subway--or above ground, if they ride the Blue or Yellow line to the airport. Instruct them to listen, just before the subway doors close, for the first two notes of "Swing Low, Sweet Chariot." The kids have four hours to return to their starting point before the system rejects their farecards.

When preparing your tourguide spiel, you gotta know, as the Music Man said, the territory.

One visiting fireman won't let me forget how we took his family down to Mount Vernon, promising in all good faith to show his little girl (the granddaughter of a dentist) George Washington's wooden teeth. Which of course weren't there. When we finally learned one of his several pairs of dentures were at the Smithsonian, we were told they were missing. The uppers have since been found, but they were never wooden.

Although Washington's dentures are hardly the reason for her visits, Nancy Reagan lists Mount Vernon as one of her favorites. She keeps up on the latest exhibits in the East Building of the National Gallery of Art, but flowers are her biggest sightseeing preoccupation, and she gets regular reports on what's in bloom around town.