1. First, read a list of fan fiction cliches, some people might detect clichés and some downvote it for clichés.
2. Don't make things happen in a zoom.
don't make something about to happen then a few words later, Zoom! it happens.
3. Don't make fanfics that are Extreme Ultra Leveled Gore seriously, it can make some people vomit due to its heavy nature.
4. Optional: Don't make something the community hates.