How to Write a Percy Jackson Fanfiction

My advice for all the newbies out there who have the inspiration and the idea but don't know where to begin. What not to do in fanfiction, in depth character studies, Mary Sues, cliches, ordering, OCs, grammar and spelling and a whole lot of puns and sarcasm. A safe haven, shall we say, for the new and inexperienced writers who want to learn.