The conservative think tank that helped guide President Reagan in his takeover of the government apparatus four years ago has some advice for political appointees in the upcoming second term.

In a report to be released Dec. 7, the Heritage Foundation advises appointees to keep career bureaucrats on a short leash and in the dark. This is to ensure that the bureaucrats don't sabotage presidential budget-cutting initiatives they oppose -- either for political reasons or because they have a vested interest in keeping the programs alive, the foundation notes.

That tough management advice is spelled out in the chapter dealing with relations between career government executives and political appointees in the foundation's upcoming book, "Mandate for Leadership II: Continuing the Conservative Revolution."

Drafts of the report were presented to top administration officials last week.

Four years ago the foundation gave the administration a blueprint for a conservative take-over of the federal bureaucracy. About 60 percent of the foundation's recommendations, ranging from military management to regulatory reforms, were adopted or implemented by the administration in its first year.

The section of the upcoming report on managing the career civil service was written by Michael Sanera, assistant professor of political science at Northern Arizona University who was formerly an assistant director at the Office of Personnel Management. His advice about keeping career executives isolated and guessing when major policy matters are being decided reflects OPM's own management style during the past four years.

Civil service executives should know "that this administration is different from the government-expansion administrations of Kennedy or Carter," Sanera said yesterday.

He said the executives will be "challenged" to recommit themselves to "the civil service idea," which he described as being able to carry out policy changes they may personally oppose or "that may affect them adversely."

The report advised political appointees to have agendas before they arrive on the job, and to constantly review those agendas to make sure they are what the president wants done.

"The political appointee without an agenda is a ready victim for the bureaucracy," the report contends. "Indeed, the 'agenda-free' political executive may compound this problem: Since he is expected to produce results, he may eagerly accept the career policy agenda for lack of an alternative."

Among the report's other advice to political executives:

*"Control over the process must be retained by the political executive and his immediate political staff. Very little information will be put in writing. Career staff will supply information, but they should never become involved in the formulation of agenda-relation policy objectives."

* Make sure that career executives know as little as possible about intended changes. "Once controversial policy goals are formulated," the report suggests, "they should not be released in total to the career staff.

"Thus, the political executive and his political staff become 'jigsaw puzzle' managers. Other staff see and work on the individual pieces, but never have enough of the pieces to be able to learn the entire picture.

"By operating in this fashion, the political executive maintains control over his political agenda and his political opponents can only guess what the political executive is after. Or they ascertain the true intention at a point in the process when it is too late to mobilize effective counter efforts."