Drawing on lessons learned belatedly in their fight against the Equal Rights Amendment, conservative political groups are uniting in a highly planned, well-financed campaign against the proposed constitutional amendment that would give the District of Columbia full voting representation in Congress.

Formal opposition to the amendment, which would give the District two senators and one or two House members, has been voted by the American Conservative Union, the Conservative Caucus, the Citizens Committee for the Right to Keep and Bear Arms, Young Americans for Freedom and the American Legislative Exchange Council (ALEC), along with individuals whose primary concerns vary from gun control, right-to-life, western land development and states' rights.

"We're not going to make the mistake we did with ERA," which was ratified by 30 states before opponents got organized, said Donna J. Carlson, chairman of ALEC, an organization of 700 conservative state legislators that is leading the opposition.

ALEC spent $15,000 this weekend to bring about 50 legislators here from 36 states for a seminar on how to stop ratification of the D.C. amendment and hear Phyllis Schlafly predict that ERA still will be beaten.

Only two states, New Jersey and Ohio, have ratified the amendment since it was approved by the Senate on Aug. 22, and opponents were told yesterday that the Ohio legislature may reconsider its decision later this month.

The money spent by ALEC -- which has a $300,000 annual budget raised from a mailing list of 23,000 conservative donors -- is more than the grand total raised so far by supporters of the amendment.

While opponents coalesce behind the fine-tuned leadership of ALEC, backers of the amendment flounder in disunity, bogged down by debates about who will direct the ratification effort and what is the best strategy to employ.

Even though proponents have seven years from last August to secure ratification by the needed 38 states, the urgency to get organized, sensed by both sides, arises from the belief that next year, perhaps even next month, could be critical to the success or failure of the amendment.

The legislatures of all states except Kentucky meet in 1979, and most of them convene in January. Although most legislatures now meet annually, many of them consider only fiscal matters in even-numbered years. Coupled with the fact that 1980 is a presidential election year, when focusing on ratification might be difficult, 1979 looms as a make-or-break period.

One strategy suggested at yesterday's meeting at the Crystal City Marriott was for opponents to avoid debating the merits of the issue.

"Debating is a no-win proposition," said Prof. Jules B. Gerard of the Washington University School of Law in St. Louis. "Be sure you don't debate the problem, debate the amendment," Gerard advised, conceding that it may be possible for District supporters to argue that they deserve some representation in Congress, but contending it is difficult for them to defend the take-it-or-leave-it amendment approved by Congress.

Patrick J. Buchanan, the former Nixon speech writer, debated the amendment with liberal columnist Tom Braden, whose appearance represented the only effort by ALEC to allow a supporter of ratification to address the workshop.

Buchanan, a third-generation Washingtonian, said that while his fellow residents have "a legitimate grievance," the District is little more than "a company town" of the federal bureaucracy.

He said the proposed amendment is "a constitutional and political disaster" that would allow "carpetbaggers" such as Julian Bond, the black Georgia legislator, to "move here and grab two seats in the Senate."

Like several other speakers, Buchanan said he would favor giving the District representation in the House only, or allowing its residents to vote for Maryland's senators and representatives. Some other opponents said they liked the idea of retroceding the residential portions of the District to Maryland, but Buchanan said he would not go for that.

"The District [would be] a small carbuncle on the otherwise smooth backside of the state of Maryland," Buchanan said.

How to deal with the racial implications of the amendment is something that has occupied discussions of both proponents and opponents.

Most of the opponents agreed yesterday that they could turn race to their advantage by suggesting that if any racist tactics are being used they are used by supporters.

Carlson, the ALEX chairman who also is a member of the Arizona legislature, said in an interview that "they raised the issue of skin color" during debate in Congress, when supporters used the pressure of black leaders to win support from certain key senators.

D.C. Del. Walter E. Fauntroy, the most visible advocate of ratification, was blamed by Braden for allowing ratification to become a partisan issue. "He has done a very good job," said Braden, who criticized Fauntroy for allowing sympathetic black Democrats to lead the ratification fight in several legislatures.

Braden said he has decided that Sen. Edward M. Kennedy (D-Mass.) "came pretty close to the mark" when, during Senate debate, he predicted that much of the opposition would stem from "the four toos" -- the belief that any senators or representatives elected by District residents would be "too black, too liberal, too urban and too Democratic."

Opponents attending yesterday's workshop all disagreed that opposition arose from the race issue. Some legislators acknowledged, however, that political philosphy, party affiliation and regional considerations contributed to their opposition.

David West, a Pheonix lawyer and former minority counsel to the House Ways and Means Committee, warned that members of Congress from the District would "join the eastern power structure that wants the west to remain the frontier." West said urban senators from Washington probably would oppose land development in the west and support claims by Indian tribes for territory and water supplies.

A Texas legislator rose to suggest that his state came into the union with the promise that it would divide into five states anytime it wanted to.

If the District gets two senators, he said, "we might go ahead and divide up and have 10 senators. And maybe two of them would be Chicanos."