PISCATAWAY, N.J. (AP) _ College student activists trying to unite campus leftists in a force for social change began a three-day convention Friday, hoping to rekindle the spirit of movements of a previous generation.

''We believe it's time to forge a more united student left so that we can be heard by those who do lead this country,'' said Stuart Eimer, a Rutgers junior and a member of the convention's planning committee. ''Historically students have played a leading role in bringing about change. We feel the time is right.''

He said about 300 students from 85 schools across the country registered for the convention but that he expected more to show up.

The delegates will get pointers from veteran political activists such as Abbie Hoffman and singer Steven Van Zandt.

The meeting will address topics such as the sale of investments in companies doing business in South Africa; on-campus recruiting by the CIA; military research conducted secretly at schools; the United States' role in Central America and the Persian Gulf; racial and sexual assaults on campuses; environmental problems; and the cost of higher education.

''This is the '80s, that's what we have to stress,'' said Eimer. ''Different issues and different history. We're proud of the continuity, of the tradition that's been established. We got a lot of help from old SDSers.

''We have a lot of activism out there, but I don't think it's reaching its full potential.''

Pamphlets for National Student Convention '88 urge the creation of a movement to realize ''our vision of equality and substantive democracy'' and rail against ''corporate and military dominance'' the activists say threaten that vision.

The activists have neither a constitution nor a name for their fledgling group.

But they said by early Monday morning, when their positions have been codified and their mission defined, they hope the result will rival the Port Huron statement, which announced the formation of the Students for a Democratic Society and helped launch student activism in the 1960s.

Allen Ginsburg was to give a poetry recital Friday night, while Van Zandt, a former member of Bruce Springsteen's E Street Band, will discuss the relationship between politics and popular culture. He produced the anti- apartheid ''Sun City'' record album.

A panel discussion with Hoffman, Van Zandt and Mark Graham, director of a nationally syndicated computer bulletin board, on Saturday evening is entitled ''The Three M's of Organizing: Media, Music and Modem.''

''Hoffman will be speaking about media, which is what he does best,'' said Eimer.

Also scheduled to appear at the convention were students from Nicaragua, El Salvador and the Middle East.