If you want to sit in on the drug conspiracy trial of D.C. Mayor Marion Barry, the U.S. Marshal's Office has three words of advice: Get up early.

The general public can expect to encounter long lines to enter the U.S. District Court building, where the trial is scheduled to begin tomorrow. The earliest among them will probably have to stand in line outside, said Chief Deputy U.S. Marshal Bill Griffin, who added that most likely the line would form at the John Marshall Plaza entrance to the courthouse.

Doors to the courthouse open at 7 a.m.

"People may not be able to get upstairs" right away, Griffin said. "There's no place for them to sit. We're not going to have them wandering the courthouse aimlessly waiting for the doors to open."

The intense interest in the Barry trial has turned the simple notion of a public trial into a logistical nightmare.

According to LeeAnn Flynn Hall, administrative assistant to Chief U.S. District Judge Aubrey Robinson, current plans call for reserving only two rows of the 10-row spectator section for the general public.

Six rows will be reserved for the media, she said, and one row will be for Barry's friends and family -- but they will have to share half the row with personnel from the U.S. Attorney's Office. The last row will be for court staff and VIPs, Hall said.

Once inside, be prepared to stay for awhile, she advised.

"Spectators will be under the same restrictions as the press," she said. "Once you're in, you're in until the break."

Security for the trial will be strict. In addition to the metal detectors at every public entrance to the courthouse, spectators will have to go through another outside the courtroom.

Deputy U.S. marshals will guard the entrance to the courtroom, she said.

Whenever members of the general public leave the courtroom, they will lose their place and have to go back to the end of the line if they wish to return.

Those stringent rules will be relaxed somewhat for the press, especially wire service reporters, who have to come and go to meet frequent deadlines.

While they are waiting in line, members of the public will have plenty of time to contemplate the courthouse itself, a vision of 1950s architectural blandness at the corner of Third Street and Constitution Avenue NW.

The building has existed only since 1952, but recent events there should qualify it for designation as a historical site.

The courtroom in which Barry will stand trial, for example -- No. 2, on the second floor -- is the same one in which the Watergate defendants stood trial in 1973 and 1974 before U.S. District Judge John J. Sirica.

The size of the courtroom was one of the major reasons U.S. District Judge Thomas Penfield Jackson decreed that the Barry trial would take place there, even though there are more spacious quarters in the building's ceremonial courtroom on the sixth floor.

"I don't want to turn this into a circus," he said last week.

"Besides, if this courtroom was big enough for Watergate, it's big enough for Marion Barry."

Much has changed since Watergate.

What was once a quiet bastion of federal justice is now much more like its urban, crowded neighbor across John Marshall Plaza, D.C. Superior Court.

In the past two years, the number of drug cases coming into the court has skyrocketed, thanks to U.S. Attorney Jay B. Stephens's policy of taking advantage of strict federal drug laws, including mandatory prison sentences.

The change in the docket has not been to the liking of many of the federal judges, who are more used to hearing civil cases or abstract issues of constitutional law.

There are other changes. Besides the metal detectors at every doorway, concrete barriers protect against car bombs. Deputy marshals patrol the halls, and they sternly clear the courtroom and the halls during recesses.

All are changes wrought by the fear of terrorism, and all have created their share of conflict -- especially between deputy marshals and journalists trying to interview trial participants in the hallway.

The changes are a reflection of the potentially dangerous cases that have found their way into the courthouse in recent years: the trial of the seven radical leftists accused of bombing the Capitol in 1983, for instance, and last fall's drug trafficking trial of Rayful Edmond III.