If Ronald Reagan's cabinet provides a clue to the way his administration will perform, it is likely to be pragmatic, hardworking and largely lacking in unconventional ideas.

The Cabinet, finally completed last week with the selection of Terrel H. Bell as secretary of education, is overwhelmingly white, male, middle-aged, professional and balanced among conflicting claims within the Reagan constituencies. For the most part, the same description could have been made of the California state cabinet during Reagan's eight years as governor.

Like President Carter before him, Reagan turned for his key Cabinet appointments to his loyal cadre in state government and to survivors of his party's last national administration.

Carter pledged to be a different kind of Democrat and then relied on the second-string of the Kennedy and Johnson administrations for several major appointments. Reagan, after promising that he would unleash the genius of the free enterprise system and bring to Washington the best brains it could provide, chose major figures of the Nixon administration for two of his top four Cabinet positions: Alexander M. Haig Jr. as secretary of state and Caspar W. Weinberger as secretary of defense. The number would have been three of four if Reagan's first choice as secretary of the treasury, John B. Connally, had been willing to take the job a second time.

Reagan's other top Cabinet selection -- William French Smith as attorney general -- is the latest entry in the old-crony sweepstakes at the Department of Justice. This, too, followed the predictable pattern of Reagan's governorship; he named his executive secretary to the state supreme court.

"Traditional" is the way one veteran Republican describes most of Reagan's choices. For the most part, this assistant to the transition thinks that the Reagan choices will perform professionally and efficiently but are not likely to make waves.

"Ron Reagan doesn't like surprises," says one of the incoming president's financial supporters. "He likes people around him whom he knows and trusts."

Of the 16 Cabinet-level selections, Smith is a personal friend and Weinberger a loyal former aide whom Reagan used to refer to as "my Disraeli." Central Intelligence Agency Director-designate William J. Casey was Reagan's 1980 campaign director. Energy Secretary-designate James B. Edwards, in addition to representing a traditional political payoff to southern supporters, backed Reagan in 1976 when his challenge to President Ford found help scarce among GOP office-holders.

Two others on the list are also loyal Reaganites -- Transportation Secretary-designate Drew Lewis, who was an effective Reagan operative at the Republican National Committee, and Health and Human Services Secretary-designate Richard S. Schweiker, who has rarely differed with Reagan since the former California governor picked him for vice president in 1976.

But Lewis and Schweiker also demonstrate the ability of Reagan to reach out beyond his natural conservative base in the Republican Party, as does the selection of James Baker III as White House chief of staff. Baker was Ford's chairman in 1976 and Lewis was the Ford campaign director in the key state of Pennsylvania. Schweiker used to be considered a GOP liberal, and he is still likely to differ with conservatives on such potentially touchy issues as health maintenance organizations.

Reagan's Cabinet selection process, and to some degree the Cabinet itself, demonstrates three Reagan characteristics that are likely to be important in the presidency: his seeming detachment from the daily business of governing, his productivity for balancing conflicting constituencies, and a somewhat contradictory tendency to cling stubbornly to a pet notion or appointment.

Reagan's detachment, so extreme in comparison to his immediate predecessors that it seems almost like indifference, was evident throughout the selection process. He considered this style a virtue as governor, when he frequently decided an issue from a narrowed list of options bought to him by aides.

But Reagan can be a hard man to dissuade when he has made up his mind about something. He hardly knew Haig personally but was convinced that the former NATO commander had the quality of professional toughness Reagan much admires coupled with a "realistic" view of Soviet military capacity and intentions. Suggestions that Haig could face a difficult Senate confirmation fight never made headway with Reagan, who was willing to fight for his first choice.

Three other Reagan selections demonstrate an executive capacity for overriding the suggestions of his staff. One is Smith, whom Reagan wanted at his side in Washington regardless of qualifications or stories about "cronyism." Another is Casey, whose energy and intellectual capacity were questioned by some of his former colleagues on the campaign staff.

The third and in a way most interesting Reagan personal choice is his only woman Cabinet nominee, Georgetown Prof. Jeane J. Kirkpatrick as ambassador to the United Nations. Reagan became interested after reading a Kirkpatrick article in "Commentary" given him by foreign policy adviser Richard V. Allen. Candidate Reagan asked to have a meeting interviewed her on his campaign plane and became personally convinced she should have a role in his administration.

What may have fascinated Reagan with self-styled "old liberal" Kirkpatrick -- the only Democrat in his Cabinet -- is that she seems to be embarked on the same long voyage from liberalism to conservatism which Reagan traveled long ago.As such, she ratifies for the incoming president one of his favorite notions, that the Democratic Party deserted him rather than the other way around.

Reagan's pragmatic tendency to be a balancer allows him to be all things to all people when the balancing works. When it doen't, as sometimes happened in the early stages of his California administration, he winds up pleasing no one.

It is too early to say whether the balancing act has failed in the crucial Cabinet posts of state and defense, but certainly there is unhappiness about Haig and Weinberger. The Haig appointment has disappointed those moderates who distrusted Nixon, supported Reagan and hoped that "Watergate" was a word they would henceforth encounter only in history books. And the selection of Weinberger, a strong defense advocate who is not likely to view waste in weapons systems more tolerantly than he views waste in anything else, justifies the always-near-the-surface suspicions of a New Right that has been given little more than rhetoric in the Cabinet selection.

Weinberger, unassailable as a Cabinet choice because of Reagan's personal trust in him, has given the New Right something to shout at by insisting on professional government troubleshooter Frank Carlucci as his deputy. This clamor on the wings could become a crescendo the first time Weinberger proposes cutting spending on any highly visible military proposal.

If Reagan runs true to form, he won't interfere with the sub-Cabinet selection, however. As a devout delegator, Reagan believes that his Cabinet officers should have the authority to name their own subordinates.

"The governor decided this was Cap's shot to call and he called it," said Sen. Paul Laxalt (R-Nev.), a Reagan confidant.

Laxalt takes issue with the notion that Reagan does not take enough interest in the presidency. Though he concedes that it was probably a mistake for Reagan not to appear with his Cabinet appointments when they were named, Laxalt says that the incoming president strongly involved himself on the key decisions. As an example he cites the selection of Interior Secretary-designate James G. Watt, a Laxalt idea put forward after former Wyoming governor Clifford Hansen found the federal disclosure requirements too rigorous.

Two Republican congressmen, John Rhodes of Arizona and Manuel Lujan of New Mexico, were on the list for Interior, but Reagan made it known he didn't want to tap the Congress. Laxalt and others on the transition team then went back "to Square One," as the senator expresses it, and interviewed a number of applicants, of whom they decided the best was Watt. Reagan also interviewed him, liked him and the choice was quickly made.

Even some staunch Reaganites who are optimistic about the competence of the Cabinet join in the criticism that the whole may not be more than the sum of the parts. It was not expected that Reagan would have more than one black Cabinet officer, but many on the Reagan team thought he would have two women and at least one Hispanic.

The answer in both cases appears to be that the Reagan team tried, but not very hard. Philip Sanchez of California was considered and Anne Armstrong of Texas was asked to serve in the Cabinet. When they declined, the spotlight shifted again to white, middle-aged males.

Nine days before Reagan's inauguration, both the Reaganites and the opposition are already making winter-book estimates on who will prove the duds and who the delights of the new Cabinet.

Rep. David A. Stockman of Michigan, the director-designate of the Office of Management and Budget, wins hands down as the most interestingly articulate Reagan choice. He is also the most pleasing to conservative theorists of the New Right, for Stockman believes in the "supply-side economics of the Kemp-Roth tax bill and is almost certain to collide with more orthodox Republican economists before the administration is many months old.

Treasury Secretary-designate Donald T. Regan is seen as the potential Walter Hickel of the Reagan administration. The reference is to the first Nixon interior secretary's independent strong-mindedness and his difficulty in being a team player.

Housing and Urban Development Secretary-desginate Samuel R. Pierce, the one black in the Cabinet, is widely considered the "sleeper" among Reagan's appointments. Pierce has impressed the Reagan transition team and the Reagan staff and may be consulted on issues beyond those involving his own department.

Progess in regulatory reform, to which he is strongly committed, is likely to be the yardstick in judging Commerce Secretary-designate Malcolm Baldridge, who also may be a gauge to the influence of his friend, incoming Vice President George Bush, within the administration.

Watt, though in some ways the most controversial appointment, also is seen as the one most thoroughly representing Reagan's own expressed views. For this reason, as well as for his articulate, conservative western views on public lands policy, the Interior Department is like to be one of the most visible battlegrounds in the new administration.

Agriculture Secretary-designate John R. Block, and to some degree Bell of the Education Department, will be judged by their constituencies on how much they deliver and by others on how much they resist the demands of agriculture and educational establishments.

Energy Secretary-desginate Edwards, who started out by repeating Reagan's vow to abolish the department he will direct, is considered the Cabinet secretary who will most quickly be in over his head.

And last, but certainly not least, Labor Secretary-designate Raymond Donavan will be watched carefully to see if he can maintain the opening to Democratic blue-collar workers that Regan developed in the campaign. The Labor Department will be an arena for important battles on regulatory reform. Donavan enters this fight as something of a mystery man who has both the good will and the skepticism of management and labor.