For the 77 new members of the House, today begins orientation week, a time to be baptized in the rituals of Washington.

For the next week, the new members will learn about everything from the Washington real estate market and potential marital problems to serving constituents and hiring staff.

And they will be wined, dined and otherwise courted by the White House, their leadership, their parties and their colleagues.

It was not always so. For many voting patterns in the House, and as a result, one House staffer said, "Everybody wants a piece of them."

The 35 new Republicans will meet at the Dulles Marriott Hotel in Virginia in a four-day orientation conducted by the Republican Congressional Campaign Committee. The 42 years, orientation consisted of a couple of seminars and a potato chips-and-pretzel reception, usually just before the new session started in January.

But the big freshman classes of 1974 and 1976 changed all that. Big new classes now have an instant impact on new Democrats will be given orientation on Capitol Hill by the Democratic Study Group and the party leadership. Later there will be bipartisan sessions put on by the Select Committee on Congressional Operations. Following that, seminars at Harvard next weekend, cosponsored by Harvard's Institute of Politics and the Congressional Operations Committee, which put up $50,000 for the seminars.

The White House will waste no time getting its point of view across to the freshman Democrats. After a session this morning on Washington real estate, the new Democrats will be whisked off Capitol Hill to the White House for a four-hour briefing on inflation, foreign policy and administration programs.

Both parties will offer the nuts and bolts of organizing an office and performing the duties of a member of Congress, but there are interesting differences between the Republican and Democratic sessions this year.

Republicans are bringing in the acconting firm of Peat Marwick Mitchell and Co. to lecture on "maximizing your time and energies. They also are bringing in two psychologists to disnew "adjusting to the demands of the new job" and "family considerations."

"Considering the rash of divorces, we thought we'd talk about some of these problems," Rick Carson of the Republican Congressional Campaign Committee said. Spouses of the new Republicans will be lectured on "image awareness."

Democrats, who were troubled by defections on key votes in the 95th Congress, will not spend time on such subjects. Instead, they will present three House leaders to discuss organization, traditions and "expectations" of Democrats in the House.

New Democrats also will be lectured on how to get the best committee assignments and on paying campaign debts.

The sessions sound mundane, but they can be crucial.

At orientation sessions in 1974, the 77 new Democrats - many elected from Republican districts - heard some innovative ways to keep in touch with their constituents, namely using a recreational vehicle as a mobile office, holding frequent "town meetings" and polling constituents on issues.

Members at the Class of 74 adopted those innovations and provided constituents with a steady stream of services. Largely as a result of that, few members of the class were defeated in 1978.