Just some tips(but also keep in mind I still have limited experience to writing).
Make characters who has depth (ambitions, intentions, flaws, driving motivation, etc..) and a plot(exposition, inciting incident, rising action, conflict, climax, falling action, resolution) , or you can make it about their life.
Briefing For Characters:
Don’t make Mary Sues, unless you’re making fun of them.
Rounded characters are fine, especially if you are using them for comedic purposes. But they also must have character depth.
Character arcs are necessary, whether it be an important and impacting revelation or just a force behind their change in character/personality. They don’t have to be drastic, a gentle arc, a bound, anything is fine, really. It doesn’t have to have an arc every chapter, after all, we don’t change or realise new things about ourselves.
A range of emotions are essential.
Briefing For The Plot:
The plot should be coherent.
A plot doesn’t have to have only one conflict, but it shouldn’t pop out of thin air.
A resolution should be satisfactory and happy endings is not necessary.
Briefing For Writing:
Make your own style.
Your writing should adapt to fit for action scenes, we don’t need you monologuing about your broken table while you’re fighting. That could be saved after the fighting.
Don’t use overused/cliché-cliché phrases. Add some of your own, add your own metaphors, mix things up.
If you use giggle in every f****** I’m leaving.
Double check your grammar and such.