After an eight-year interruption to run American foreign policy. Henry Kissinger returned to academic life yesterday at Georgetown University, attracting crowds of friendly students and trailed by reporters and Secret Servicemen.

The former Secretary of State refused to comment on the Carter administration but in a brief talk Kissinger said:

"The fundamental problem of the United States is to find some relation between our value and our possibilities . . . We have to avoid Quixotic crusades that will sap domestic support and the possibility of (achieving) an international consensus. But we must also avoid conducting a foreign policy (based) on the practical considerations of the moment."

"The concerns of the United States are not defined by a particular administration," Kissinger added, "but by the reality within which we live."

Kissinger came to Washington in 1969 as President Nixon's national security advisor after teaching for 18 years at Harvard University. Yesterday, well-tanned after a vacation in Acapulco, he began six months as a visiting professor at Georgetown.

As he walked across campus a procession of reporters and television film crews scurried behind him, and when he went into different buildings, hundreds of students waited outside. Most cheered when they saw him and clamored for autographs.

"I haven't had any contact with students for eight years," Kissinger told a small group in the office of Dean Peter Krogh, the head of Georgetown's School of Foreign Service. "I look forward to that opportunity."

University officials said Kissinger is scheduled to give only one public lecture and to appear in just three classes and seminars. They said he will spend most of his time doing research and writing at Georgetown's Center for Strategic and International Studies at 1800 K Street, NW, where he has already moved into a large office.

The university is paying Kissinger $155,000, but he also reportedly has made a $2 million arrangement to write his memoirs.

"He's not doing that much at the university," said Paul Anderson, a graduate student as he waited on the steps of an administration building while Kissinger attended a champagne reception inside for trustees and a few students. "I wish he was getting more exposure to students."

A few minutes earlier, Kissinger had walked into a fifth floor smoking lounge in the university library and asked some students how they were getting along. He was quickly surrounded by reporters, asking him questions about foreign policy, which he deflected politely.

"I walked in here to buy some Lifesavers," one student exclaimed. "And I ran into Henry Kissinger. It's fantastic."