It was, one man said yesterday, "a historic occasion:" Charles S. Robb, the first person from the Washington suburbs elected governor of Virginia, had come to McLean seeking people and ideas for his new administration.

Home builder Myron P. Erkiletian surveyed the crowd around the long table at the McLean Community Center and said he saw "a lot of mouths at the trough."

All of them had been invited by Robb, who lives in McLean, to help him locate the people he will name to top patronage jobs in the first Democratic administration in Richmond since 1969.

For some it was a new experience.Sharon E. Davis, head of the Arlington Democratic Committee, wasn't sure what Robb expected. "We've never done this before, and we're not sure what's out there," she said.

Robb quickly laid out his ground rules. "I promise no bias in favor of Northern Virginia," he said. "But the very fact that the governor lives here, and will continue to maintain a home here, means that he begins with an awareness of the area's problems."

Residents of the Virginia suburbs long have complained that their needs were inadaquately understood and served by downstate politicians. In the past, Robb said, few area residents were offered state jobs. That will change when he takes office Jan. 16, the governor-elect said. "Northern Virginia will be fairly represented, to say the least, on the boards and commissions."

Some of the supplicants who met with Robb yesterday came armed: John Quackensbush, secretary-treasurer of the Washington Building Trades Council, demanded the firing of the Republican state secretary of labor and industry; Fairfax County Board Vice Chairman Martha Pennino turned over a wish list of pet projects and prospective employes, and three representatives of the Council of Senior Citizens pleaded with Robb to continue programs for the elderly that are being eliminated by the Reagan administration's budget cuts.

Another Fairfax supervisor, Joseph Alexander, told Robb there is "a distrust of state government, especially of the highway department, by local officials." Alexander, currently the chairman of the Metro transit board, reportedly is lobbying for a spot on the highway commission, whose recent actions selecting a route for the proposed Springfield Bypass in Fairfax angered many county officials.

After the meeting, Robb was asked if he might try to overturn Gov. John N. Dalton's two recent nominations to the highway panel. Robb replied that "it is an open question" whether the Democratic-controlled General Assembly would attempt to block nominations before they expire in eight months.

Some top Democratic legislators have suggested that the assembly may simply refuse to act on Dalton's final nominations, allowing them to die with the onset of the Robb administration. "We just won't confirm them," said Del. Theodore V. Morrison Jr. (D-Newport News). "There's no point in embarrassing them."

Robb said the cap on state pay may thwart his recruiting efforts. "The question will be can we entice them to give up lucrative positions in the private sector" for the top 200 jobs that pay a maximum of $59,000, he said.

One area where a financial sacrifice is not required, Robb said, is academia. "Unfortunately, the salaries there are not that high," he said, nodding in the direction of two state college presidents, George Johnson of George Mason University and Richard J. Ernst of Northern Virginia Community College.

The governor-elect said he hoped that some of people invited to yesterday's meeting, and to earlier ones in Richmond, Tidewater and Bristol, might be interested in the jobs. Those in the private sector, he suggested, might consider nominating their competitors, a tactic that Robb said offers "the double reward of providing superb service to the state and reducing your own competition."

Most of the patronage jobs available, according to David McCloud, Robb's transition chief, are the 1,000 or so positions on state boards and commissions that are largely voluntary, paying only expenses for travel and meeting days. Nonetheless, McCloud said, his office has been flooded with resumes "from all corners of the state, and beyond."

Robb would not say whether he might tap former national Democratic officials or other out-of-state residents for any of the top positions. He said he doesn't plan to begin his own review of the applicants until next week.