Deputy Secretary of State Warren Christopher held a 50-minute briefing for representatives of the families of the 52 American hostages yesterday, describing the procedures by which the negotiations between the United States and Iran are being conducted, but cautioning the group against renewed optimisism about a possible early release of their relatives.

"He described to us the procedure by which they are doing these negotiations," said Louisa Kennedy, the spokesman for the Family Liason Action Group (FLAG), an umbrella organization representing the hostages' families. " . . . But I think their general word to us was 'Don't get your hopes up.'"

The meeting in Christopher's office was called at the request of FLAG's leaders, and included eight of the nine members of that group's board of directors. After the meeting with Christopher, the hostages' relatives met with other State Department officials for a discussion of the provisions of the Hostage Relief Act, which was signed into law by President Carter last month.

Under the provisions of this act, the hostages' families are exempt from most federal income taxes and are eligible to receive both medical and educational benefits from the federal government. The regulations to put the act into effect have not been drafted, however.

According to State Department spokesman Joe Reap, yesterday's meeting was "one in a series of periodic briefings" of the hostages' families.

Interviewed shortly after the meeting, FLAG board member Dorothea Morefield said she was glad Christopher had conducted the meeting. Asked if the meeting had left her more optimistic, she shook her head and said, "I'm waiting. It's a waiting process."