George Bush polished his inaugural address Tuesday, trying to make it shorter, while the Senate opened the first confirmation hearing for his Cabinet and the capital was rehearsing ceremonies marking the change of power at the White House.

Three days before Bush will be sworn in as the 41st president, hotels were filling up with early arrivals from the 300,000 people expected to watch or take part in the five-day extravaganza."The mood is very upbeat," said Ed Cassidy, a spokesman for the inaugural committee. "Rehearsals are taking place all over town. Decorations are going up. Thousands of media people from all over the world are picking up their credentials" to cover the inauguration.

On Capitol Hill, James A. Baker III, picked by Bush to be his secretary of state, went before the Senate Foreign Relations Committee to testify about his nomination. Demonstrating bipartisan pride in a native son, Texas Sens. Phil Gramm, a Republican, and Democrat Lloyd Bentsen sat alongside Baker at the witness table and urged that he be confirmed.

Baker testified that the first order of business for Congress and the new administration is a "meeting of our minds on how to proceed with a changing Soviet Union." He said, "Our task is to arrange affairs so that whatever the outcome of perestroika, a more responsible, constructive Soviet policy will remain in Moscow's interest."

Baker also said the United States cannot abandon the Contra force opposing Nicaragua's leftist Sandinista government.

Baker's confirmation hearing, expected to run two days, is the first for any member of Bush's Cabinet. The next round begins Thursday when the Senate Labor Committee meets on the nomination of Elizabeth Dole as labor secretary and the Governmental Operations Committee hears testimony from Richard G. Darman, chosen as Bush's budget director.

Other hearings will follow in quick order. None of the Cabinet nominees is expected to encounter much difficulty winning confirmation.

"They are generally experienced, hopefully pragmatic people, and we won't have the rigid ideology of the first Reagan term," said Senate Majority Leader George Mitchell, D-Maine.