* Age categories: Level I, 5 to 9; Level II, 10 to 15; Level III, 16 and older. The writer's age on Feb. 19, 1992, will determine their level.

* Story lengths for the three levels are: Level I, 250 to 500 words; Level II, 500 to 1,000 words; Level III, 1,000 to 2,000 words.

* Proper spelling and grammar are important and will be judged. The story must be typed or printed clearly.

* Each story must have a cover sheet listing the entrant's full name, address, phone number, birth date, names of parents or guardians, name, address and phone number of school attended, name of teacher.

* Students should keep copies of the story.

* Stories must be postmarked by Feb. 29, 1992. Finalists will be interviewed at home or school to make sure the story is actually the work of the student and not a well-meaning adult. Stories determined to have been substantially composed by an adult will be disqualified.

* For further details call the Mystery Loves Company Booksellers, 1730 Fleet St., 276-6708. Book store hours are: 11 a.m. to 6 p.m. Tuesday through Saturday, noon to 5 p.m. Sunday.