A jury of seven men and five women was chosen yesterday for the trial of former White House aide Lyn Nofziger and his partner, Mark Bragg.

Opening arguments before U.S. District Court Judge Thomas A. Flannery are scheduled to start Tuesday at 9:30 a.m.

Nofziger is charged with four counts of illegal lobbying for clients of a consulting firm that he opened here with Bragg after resigning as assistant to the president for political affairs in 1982. Bragg was charged with aiding and abetting Nofizger in one instance involving the now bankrupt Wedtech Corp.

Conflict-of-interest law prohibits former high-ranking government officials from lobbying at their old agencies on certain matters for a year after leaving.

The jury and six alternates were picked after four days of questioning about their attitudes toward the Reagan administration and their awareness of "alleged improper conduct" by administration officials.

The regular panel includes an art teacher, a court messenger, a man who once pleaded guilty to misdemeanor charges of shoplifting and cocaine possession, a retired teacher, a Federal Reserve security guard, a speech-language pathologist and a Postal Service review clerk. Eleven are black. One is white.

The trial is expected to last four to six weeks. In a last-minute memo filed yesterday, independent counsel James McKay, directing the prosecution, asked the court to prohibit defense lawyers from asking prosecution witnesses about attempts by San Francisco lawyer E. Bob Wallach to lobby the White House for Wedtech.