Going shopping or just browsing at Brooks Brothers here was once both a ceremony and an adventure.

First you had to find the place, which wasn't easy if you hadn't been there before. The dignified brass letters -- set into the wall next to Duke Ziebert's restaurant on L Street NW, just west of Connecticut Avenue -- mystified some passersby.

Initiates, however, knew that one flight up were the proper trappings for any situation.

An elevator ride was almost sacrosanct, not because the steps were steep, but because the conveyance was one of Washington's last elevators with its own polite operator.

But "Watch your step, please," is about to be eliminated from the Brooks Brothers experience. The Washington store of the New York-based chain (which in turn is owned by a Washington firm, Garfinckel, Brooks Brothers, Miller & Rhoads) is moving several bocks west -- and down to earth.

Construction workers are putting the final touches on the new Brooks Brothers store, located in the ground floor level at the southeast corner of 19th and L Streets NW. When the doors open on May 10, a new chapter will begin in the store's long history.

"This new location is a permanent location," said Bob Bates, manager. "The new store will offer us an opportunity to create a more stimulating and comfortable shipping environment, the ability to show our merchandise more effectively . . ."

Creating that environment will take Brooks into previously untried territory here: It has never even had a display window. Walk-in customers will be a new clientele. And competition, at many stores, is nearby.

The move west will almost double the sales floor area of the store. And a few new full-time employes will come aboard. The walls will still be trimmed in understated hardwood, the floors covered with padded gold carpet.

Also unchanged are the principles that have made Brooks Brothers a success since 1818. As Garfinckel corporaiton President Manuel Rosenberg said recently: "Brooks Brothers, which has withstood the test of time, and the test of all kinds of fashion change in men's apparel, has been, is and will continue to be less than conservative. Less than conservative in its drive for business and for growth."

Corporate expectations for the new Washington location are less than conservative also. "Basically we think eventually we'll at least double our business by moving. In the first year we expect a substantial increase in volume," commented Frank T. Reilly, president of Brooks.

"We have no specific plans for additional expansion in this market, but we have been looking at locations for a year or so," Reilly said. "The most likely area would be around Chevy Chase."