Good advice for would-be novelists; Guide to Fiction Writing, by Phyllis A. Whitney. Boston: The Writer (8 Arlington Street, 02116). 133 pp. $12.95.

Phyllis Whitney, a best-selling fiction writer who never went to college, has written a tonic of a book for the working writer and the writer who concedes that writing is work.

Miss Whitney's first piece of advice -- do not expect immediate success. Her own came after years of rejection slips, first being published in pulp magazines , then graduating to the genres for which she is now best known -- mysteries and romance novels.

Her next maxim is crucial -- pay no attention to the ''temptation not to write.'' Discipline, regular work habits, making the effort to get something down on paper, make the difference between the person who merely fantasizes and the person who can produce a finished manuscript.

She suggests the use of a fine tool -- the keeping of a notebook -- which serves the writer simultaneously as a practice arena and as a place to set down sketches for characters, settings, even descriptions of time of day and weather. And she dissects and analyzes the elements that contribute to successful fiction that holds the attention of readers.

Miss Whitney is reassuring about the sustained effort it may require to develop a plot and to link a succession of fictional ideas. For, she admits, there are times when even a seasoned writer may feel he has no ideas. Always, she remembers the reader and points out gently but firmly that if a writer's manuscript fails to satisfy and no editor wishes to take it on, it is time to return to the typewriter.

In sum, a helpful and pleasingly astringent message for writers who really intend to write.