WHEN YOU'RE William F. Buckley Jr., editor of the National Review and with certain standards to maintain, what other way is there to introduce your top editor in Washington, John McLaughlin, than in Latin?

"Nos non morituri vobis salutamos," Buckley began last night as the president of the United States and almost everybody else in the Madison Hotel's Dolley Madison Room listened for all they were worth to catch at least one recognizable word. It came in the next burst.

"Non salutamus Salt Two. Non salutamus Tipus O'Neill, non alterii Tipus O'Neill. Non salutamus Fritz Mondale non presidentabile . . ." Buckley continued, and some people, including the president, began to relax noticeably.

Loosely translated, what Buckley said, as he worked his way up to McLaughlin, was, "We who are not about to die salute you," making it clear in the next breath that he was not saluting "Tipus O'Neill," or any other Tipus O'Neills and certainly not Fritz Mondale, who officially announced his candidacy yesterday, for president.

But he was there to salute conservative commentator McLaughlin, a former Jesuit priest and Nixon speechwriter, who will become National Review's executive editor in Washington.

For Latin purists, Buckley later dismissed his linguistic acrobatics as mere "made-up kitchen Latin." Inexplicably, his remarks were typed on White House stationery.

Snaring Ronald Reagan as First Guest seemed only just for Buckley and Co. after the clerical mix-up by then-President-elect Reagan's staff more than two years ago that found the National Review's very own standard bearer missing from its 25th anniversary party. At the time, Buckley was crushed.

"The only one he's ever missed," Buckley said last night.

Reagan more than made up for it last night, despite any problems he may have been having lately with the conservative wing of his party. In the dual role of Bill Buckley's First Disciple and National Review's First Fan, the president came laden with praise for Buckley and his magazine. Reagan said he often wishes he had Buckley as an interpreter when faced with some bureaucratic memos.

"A fellow comes in, hands you a memo and waits while you read: 'Action-oriented orchestration innovation was generated by escalation of decision-making dialogue . . .' I take a chance and say 'Let's try busing,' " said the president. "If he walks away, I know I guessed right."

And speaking as National Review's First Fan: "Today we celebrate Washington's birthday and I can't think of a more appropriate occasion to celebrate National Review's heightened profile in the nation's capital, for if George Washington was the father of his country, the National Review has been the father of the intellectual conservative movement.

"National Review isn't my favorite because it's fought the good fight so long and so well, although that would be reason enough. It's my favorite because it's splendidly written, brillantly edited and a pleasure to read. In fact," said the president, "I honestly believe that even if I were to suffer mental illness or convert to liberalism for some other reason, NR would still be my favorite magazine."

For conservatives, at least, the party was without question the place to be.

"On a scale of one to 10, you have to rate it a 10," decided conservative direct-mail wizard Richard Viguerie. "I can't remember a Washington party I've been to when I've known 80 percent of the people."

Faces in the crowd: attorney Richard Moore, journalist Pat Buchanan, author Victor Lasky, former ambassador Clare Booth Luce, former congressman Ed Derwinski, senators John East and Jeremiah Denton, public relations consultant Joe Canzieri, presidential assistant Ed Hickey, attorney Richard Allen, Arab League envoy Clovis Maksoud, Energy Secretary Donald Hodel and Interior Secretary James Watt. Not to mention Yale's own Whiffenpoofs, flown here especially to sing for the guests.

"I'm always at home with these people," said Watt.

Others on the program included NR's publisher William A. Rusher; managing editor Priscilla L. Buckley, who is Buckley's sister; and senior editors Richard Brookhiser, Jeffrey Hart and Joseph Sobran.

For McLaughlin, the evening represented the better of two worlds: being "in" with Bill Buckley rather than "not being in." McLaughlin said it reminded him of a time in 1974 when fellow Nixon speechwriter Pat Buchanan wrote Buckley to suggest that he consider putting McLaughlin on Buckley's TV program, "Firing Line."

A couple of weeks later, Buckley replied:

"Dear Patrick, Intending No disrespect, WHO/ IS/ JOHN McAlguhlin? As ever, Bill."

The letter was a bit of a surprise for Buckley, who didn't know until last night that Buchanan had framed it and given it to McLaughlin several years ago.

McLaughlin will direct National Review's first office in the nation's capital. Asked how he felt about being Washington editor for the president's favorite magazine, he paused.

"Well," he said, "you think twice."