A presidential task force seeking ways to improve the Defense Department's management and contracting practices met with President Reagan yesterday to, in the words of its spokesman, "discuss its mandate."

Herbert E. Hetu, spokesman for the President's Blue Ribbon Commission on Defense Management, said the 15-member panel also has scheduled meetings and briefings with top Pentagon and congressional leaders over the next three days.

The panel, headed by industrialist David Packard of the Hewlett-Packard Corp., was created by Reagan on June 17 in the wake of congressional and public outcry about spare parts "horror stories" and waste in the military.

It held its first organizational meetings in August and, according to Hetu, was prepared to discuss a "plan of action" with the president, national security affairs adviser Robert C. McFarlane and Defense Secretary Caspar W. Weinberger.

It will receive briefings from John E. Smith, the Pentagon's director of major system acquisition, and Brig. Gen. Richard B. Smith, deputy chief of staff of the Air Force for contracting and manufacturing.

On Thursday, the commission will be briefed by Joseph H. Sherick, the Defense Department's inspector general; Donald B. Rice, president of the Rand Corp., and Michael D. Rich, manager of Rand's resource management program, Hetu said.

The panel hopes to offer some interim recommendations by the end of the year and to complete its work by next summer.