Ronald Reagan, the darling of the Republican Party's right wing, reached out today to an unusual ally - the National Association for the Advancement of Colored People - in criticizing President Carter's domestic policies.

Citing the NAACP's opposition to the administration's energy plan, Reagan accused the President of siding with "elitist" social planners bent on slowing economic development and thus denying low-income groups a chance for more prosperity.

"The limits-to-growth people who are so influential in the Carter administration are telling us, in effect, that the American economic pie is shrinking, that we all have to settle for a smaller slice," the former California governor said.

"I believe black Americans want what every other kind of American wants: a crack at a decent job, a home, safety in the streets, and a good education for out children," he continued, "and the best way to have those things is for government to get out of the way while the rest of us make a bigger pie so that everybody can have a bigger slice."

Reagan spoke to about 300 people at a $25-a-person luncheon during a day-long series of political workshops sponsored by Citizens for the Republic, the political action group that he founded and is using to keep his presidential aspirations alive.

The purpose of today's meeting, the third the organization has held around the country, was nuts and bolts politics, with seminars on such topics as publicity, direct mail advertising and political organization. A Reagan associate said that Reagan and other conservatives have suffered in past campaigns from a lack of such practical expertise among their supporters.

But the conservative ideology that impassions Reagan's supporters surfaced throughout the day. A woman complained about a lack of discussion about the "issues." And when Reagan opened the luncheon to questions, they all concerned the one issue that revived his 1976 GOP primary campaign and nearly propelled him to the presidential nomination - the Panama Canal treaties.

In brief interviews, both Reagan and Sen. Paul Laxalt (R-Nev.), his 1976 campaign chairman, discounted the strong positive reaction Carter received Thursday when his State of the Union address to Congress called for approval of the treaties.

"Oh sure, he had a majority there, but we're not talking about a majority, we're talking about a two-thirds majority," Reagan said.

Laxalt, a member of a so-called "truth squad" that has been traveling the country in opposition to the canal treaties, also downplayed the importance of the willingness of Senate Minority Leader Howard H. Baker, Jr. (R-Tenn.) to support the treaties with certain changes. He told the luncheon audience his travels had convinced him that the American people "are more strongly opposed to these treates than ever."

The luncheon attracted a number of conservative Republican political figures, but it was Reagan the audience came to hear.

Sen. Richard Schweiker (R-Pa.), Reagan's choice for vice presidential running mate near the close of the 1976 primary campaign, brought the audience to its feet cheering when he declared that polls show "a lot of people want to fire Jimmy Carter" and that Reagan is the one who has "the ability, the experience and the charisma to do just that."

Other speakers struck much the same theme - that the President is his own worst enemy, or as one of them said, "The best thing we've got going for us today is in the White House."

Party chairman Bill Brock has been seeking to attract black voters to the GOP, and Reagan's linkage of his conservative philosophy with the NAACP's stand on energy fits that strategy.

"We're not the party of big business or the country club set," the Californian said. "We're not a narrow band of ideologues trying to take over the majority . . . there is a new majority out there."