Martian Manhunter: The Case For A DCEU Film

No. 4:  Give the Background in the First Act

Always keep the character origin confined to the first act. From there the rest of the action movie should be purely linear. For instance, the beginning of the film could have J'onzz explain what brought him to Earth (in most versions of his story his species is wiped out on Mars). Then periodically through the first half include flashbacks of him realizing what impact his powers have on earth, and understanding his purpose. This trope tends to be pretty standard in superhero movies, just look at Batman Begins and Man of Steel. Still, origins are important when average viewers are not familiar with characters storylines.