Paul Levitz probably thought about what a comic book writer does more than any of his contemporaries, or mine, and during his dozen-plus-years stint as writer of The Legion of Super-Heroes, systematized what his predecessors did haphazardly, if at all. Then, as an aid to his own work, he created three versions of the Levitz Grid  Basically, the procedure is this: The writer has two, three, or even four plots going at once. The main plot—call it Plot A—occupies most of the pages and the characters‘ energies. The secondary plot—Plot B—functions as a subplot. Plot C and Plot D, if any, are given minimum space and attention—a few panels. As Plot A concludes, Plot B is „promoted“; it becomes Plot A, and Plot C becomes Plot B, and so forth. Thus, there is a constant upward plot progression; each plot develops in interest and complexity as the year’s issues appear.
Additionally check out The Levitz Paradigm: „The best imitation of life possible in a work of fiction“