Vice President Bush has been moving on several fronts this week to bolster his staff and lay plans for his expected presidential campaign in 1988.

Yesterday, Bush completed a shakeup of his top assistants. He named Frederick N. Khedouri, associate director of the Office of Management and Budget, to be his deputy chief of staff and policy director, working under chief of staff Craig L. Fuller.

Khedouri has been a key deputy to OMB Director David A. Stockman and particularly influential in energy, natural resources, agriculture and space policy.

Marlin M. Fitzwater, now a deputy White House press secretary specializing in domestic policy and economic issues, will become Bush's press secretary, replacing Peter Teeley, who left to open a consulting firm.

Associates say Bush also is attempting to define his vision of where the country should be going later in this decade. To that end, he met this week with author and futurist Alvin Toffler for a discussion that included pollster Robert Teeter and political strategist Lee Atwater, former deputy director of the Reagan-Bush campaign committee.

Sources said Bush also plans to form a political action committee by late spring to help congressional candidates in the midterm campaigns and serve as a base for his 1988 bid. Rival Republican Rep. Jack Kemp (N.Y.) already has such a committee.

One official said the committee would be patterned on one Reagan established in the years before his 1980 campaign.

Bush has not declared his 1988 candidacy but all indications are that he plans to run. Reagan has given Bush lavish praise but stopped short of an outright endorsement.

The staff changes are effective April 1, when Fuller becomes chief of staff. He previously was White House Cabinet secretary.

Fitzwater has been the chief assistant to White House spokesman Larry Speakes for domestic policy and economic issues. He previously was a Treasury Department spokesman under Donald T. Regan, now White House chief of staff.

It also was announced that Joan M. McEntee, one-time chief counsel and staff director of the Senate Governmental Affairs Committee, was appointed staff assistant and deputy to Fuller.

Appointed deputy assistants to Bush were Thomas J. Collamore, who will be staff secretary; Andrea L. Fischer, scheduling; and David J. Ryder, advance. C. Boyden Gray, Bush's legal counsel and deputy chief of staff, becomes counselor to the vice president; and Jennifer A. Fitzgerald remains executive assistant but will become Bush's assistant for legislative affairs, working out of his Senate office