On the Friday that President Carter announced his proposed budget cuts, Ronald Reagan's domestic adviser, Martin Anderson, slipped away from the candidate's party at the Mattoon, Ill., airport and placed a telephone call to San Francisco.

After a chat with Milton Friedman, the nation's best-known conservative economist, Anderson emerged with information that would enabale Reagan to tell reporters later that the budget cuts, while a step in the right direction, were inadequate to control inflation.

The same day, Rep. Thomas B. Evans Jr. (R-Del.) had an idea. He told Reagan that the United States could increase its influence among the "captive nations" of Eastern Europe by expanding the Voice of America, Radio Free Europe and Radio Liberty.

This suggestion showed up intact the following Monday in a foreign policy address Reagan made in Chicago and again, immediately afterward, in a speech that was warmly applauded by a group of Polish-Americans.

These two incidents typify the way ideas and information are flowing into the Reagan campaign as the candidate's focus shifts from the Republican primaries to an anticipated contest with Carter.

Only a few months ago, Reagan was a candidate who wrote his own one-liners and drew a seemingly endless supply of statistics from newspaper clippings he found himself.

Now, the former California governor has briefings or telephone conversations regularly with such economists as Friedman, Alan Greenspan, Jude Wanniski, and Arthur Laffer. He is drawing on the diverse expertise of such men as former treasury secretaries George P. Schultz and William E. Simon, former Federal Reserve Board chairman Arthur F. Burns, former Arms Control and Disarmament Agency director Fred C. Ikle and former health, education and welfare secretary Caspar W. Weinberger, who was Reagan's state finance director in California.

Reagan also is relying increasingly on the advice and staff work of key Republican politicians such as Evans, Rep. Jack Kemp of New York and Sen. Paul Laxalt of Nevada.

Out of the eclectic consultation, some new themes and proposals are beginning to make inroads into Reagan's stock antigovernment speech.

In New York this week Reagan used information from Kemp that enabled him to demonstrate newfound knowledge about New York State's taxation and inflation burdens. In the same speech he took heed of inner-city unemployment problems with information provided him by New York political director Roger Stone.

And Reagan's foreign pronouncements, while still stressing the perfidy and military might of the Soviet Union, increasingly have begun to reflect Ikle's influence that a U. S. military buildup can be used as leverage for genuine arms control.

Reagan also is obtaining a broad range of information from GOP members of Congress scrambling to board the Reagan bandwagon before it gets too far along.

Four years ago, when Reagan was running for the Republican nomination against Gerald Ford, virtually all his congressional help came from Laxalt, governor of Nevada when Reagan was governor of California. Laxalt remains the GOP officeholder closest to the candidate, but 13 other senators, and dozens of the House members are now supporting Reagan.

"We have key people on all committees who can provide expertise from a realistic political standpoint," Laxalt says.

As Laxalt sees it, such communication is as important for Congress as for Reagan. With this in mind, Laxalt conducted a congressional briefing last fall and intends to bring Reagan to Washington for another congressional meeting in April.

"Obviously, a potential problem would be that you would have another Carter who could not work with or appreciate the Congress," said Laxalt. "I don't want him, if he is elected, to be a stranger to the Hill."

Directing the flow of information to Reagan is chief issues adviser Edwin Meese III and two senior staff consultants, Anderson on domestic policy and Richard V. Allen on foreign policy. At least one of them travels with Reagan throughout the campaign. A fourth frequently consulted adviser, who rarely travels, is Richard J. Whalen, president of Worldwide Information Resources.

Except for Meese, who was executive secretary to Reagan during his most successful period as California governor, there is a common thread to the background of these key advisers. All were young program-oriented aides in the salad days of the Nixon administration when people talked about welfare reform rather than Watergate. All, like departed Reagan campaign manager John Sears, left the Nixon White House after policy or personal disputes with top presidential advisers.

Whalen, a former editor of Fortune, wrote a searing book on administration failures titled "Catch a Falling Flag." Economist Anderson, an architect of the all-volunteer Army and author of books on welfare reform and urban renewal, left Nixon in 1971 to join Stanford University's Hoover Institution on War, Revolutionand Peace. Allen, once regarded as the right-winger in residence at the National Security Council, departed early in the Nixon administration only to return in 1971 as deputy assistant for international economic affairs.

It is an open secret that Allen, like others at the NSC, resented the control of information and access to the president monopolized by Henry A. Kissinger. Without mentioning Kissinger by name, Allen says he has learned from his White House experience and tells consulting academics that information they provide for Reagan will reach the candidate unaltered and with the author's name on it.

"Information flows through me to the candidates where it's in accord with what he feels or what I feel," says Allen."We've had too many bad examples of what can happen when it's the other way."

Meese, a San Diego lawyer, is the glue that holds the Reagan senior staff together. He is easygoing and so trusted by Reagan that he does not need to guard proximity to the candidate in order to wield power.

"My role is to direct the process, to see that there aren't issue questions left unanswered and to make sure that the information that comes in brings different points of view," said Meese.

Because of this attitude and because of Reagan's accessiblity to his staff, says Anderson, "there's suprisingly little jockeying to be near the governor since everyone knows they can talk to him if they need to."

Outside his immediate circle, which on a consultative basis also includes long-time former California aides Peter Hannaford and Michael K. Deaver, Reagan probably relies most on Simon, Laxalt and Kemp.

Simon and Reagan were social friends and politicial allies, but their relationship stopped in 1976 when Simon was campaigning for Ford. Assured that Ford would not run again, Simon joined the Reagan campaign at announcement time last November and has been a valued consultant ever since.

It was Simon who brought in William J. Casey, now the Reagan campaign manager, to advise the candidate on economic and regulatory issues. Simon said he did not know Sears was to be ousted but thought "it would be ideal to have John on the political side and Bill on the administrative substantive, financial side."

Simon says he is concerned that Reagan's understanding of issues be deep enough so that he will "not be called shallow or jingoistic as he has been."

This concern is not limited to Simon. At many levels of the campaign there remains a nagging worry that Reagan has not yet grasped many important technical issues and a related concern that, even when he does, he relentlessly oversimplifies them. But there is also the belief that the candidate can and will reach out to absorb the information he needs if enough is made readily available to him.

"The basic approach we're taking is that ther is no one economic adviser, no one foreign policy adviser," Anderson said Friday in Palo Alto before leaving on Reagan's latest campaign trip. "With the complex problems we're facing, we need a large and talented group of people around at all times."

Kemp and his ally Wanniski, who were brought into the campaign by Sears, have been influential in Reagan's decision to opt for the "supply-side economics" embodied in the Kemp-Roth Bill. This view holds that a large tax cut will stimulate production, expanding the tax base so that the government will collect additional revenues even though the tax rate is lower.

Anderson made a similar advocacy in a memo last August and there has been no philosophisical disagreement within the campaign over Reagan's support of a 30 percent income tax cut phased in over three years.

"Our adversaries are not people who believe differently but people who are not involved in ideas and want him [reagan] to be cautious because he's doing so well," Wanniski said.

Kemp and Wanniski were two of a score of outside experts who briefed Reagan during a three-day meeting at a Los Angeles airport motel last January.

Over a sandwich lunch, recalls Wanniski, Reagan showed his receptivity to the Kemp-Roth idea by describing what happened in the movie industry when taxes increased.

"Back in '36, we used to make three or four or five movies a year and we loved it," Reagan was quoted as saying. "But in 1940 the wartme emergency surtax went up to 96 percent at the top of the scale and my agent told me, 'you can't make more than one movie a year.' So what happened is that instead of working for the whole year, we sat around the Brown Derby looking for oil deals."

On foreign policy and national security issues, the two experts most frequently consulted by Reagan or by Allen in his behalf are Ikle (pronounced ee-clay) and William R. Van Cleve, director of defense and strategic studies at the University of Southern California.

The influence of the Swiss-born Ikle, onetime head of the Rand Corporation's social science department, has shown up in Reagan's criticism of "mutual assured destruction" nuclear policies and in Reagan's call for concerted action in the Middle East against Soviet expansionism.

"We in the United States must marshal the strength to back up the self-defense of all independent nations in the Middle East," Ikle wrote in The Washington Post earlier this year in words similar to those since used by Reagan. "And the leaders of these nations must rise above the destructive fanaticism of a Khomenini. In the life of nations a mortal threat can call for the greatest acts of statesmanship -- provided the threat is recognized."

Both Ikle and Van Cleave were among the seven foreign policy experts whom Allen brought in to brief Reagan at a March 10 meeting at the Atlanta airport.

The other briefers included two fairly regular consultants, Lt. Gen. Daniel O. Graham (Ret.), director of the Defense Intelligence Agency from 1974 to 1976, and Joseph Churba, president of the Center for International Security in Washington. Also attending were Raymond Tanter, a professor of political science at the University of Michigan; Robert L. Pfaltzgraff Jr., professor of international politics at Tufts, and Michael P. Pillsbury, a national security adviser to a Senate steering committee.

Reagan also has consulted with Robert Stausz-Hupe, former U.S. ambassador to NATO, and with two Democrats: Henry Rowen of the former president of Rand, and Eugene V. Rostow of Yale, a member of the anti-SALT Committee on the Present Danger.

In no case, said Allen, does Reagan ask any of these experts for political support.

"We are looking for information, not endorsements," Allen said.

Most of the advisers in both foreign and domestic policy would be classified as conservative, though there is a wide range of disagreement on specific issues. Reagan sometimes widens the range, as he did when he rad an article he liked, "Dictators and Double Standards," in Commentary magazine.

The candidate sent a note of praise to the author, Hubert Humphrey Democrat Jeanne Kirkpatrick of Georgetown University. He then asked Allen, who had given him the article, to set up a meeting with the author.