User blog:TeamTaycobSoDealWithIt/Any advice on how to write a fanfic?

So I am writing my first piece of fan fiction, if an already-written parody (or three and one-third) does not count. I already know almost exactly how I want things to happen, which is the equivalent to a failure for me because I suck at pre-planning everything in a novel, but I am stuck on how it should begin. It is sort of an anti-fan fiction piece too, if you look at it from a certain way. It is a fanfic on how Bella and Edward's relationship could be like in reality with no vampires, no werewolves, and just humans. Anyway, I have no idea how it should begin. Should I just start with something random and see how the story flows? What should I do? Can anybody spare me some advice on how to write this fanfic? Please, people. It would help a lot!

-TeamTaycob