1) Write the story out, ignoring all plotholes, spelling mistakes and repetitions.
2) Remove the repetitions, plotholes and spelling mistakes
3) See what needs expansion and expand it, such as descriptions of places or giving background details of the world/environment/person
4) Prune it...severely.
5) Edit it for mistakes, errors
6) Put it in a drawer and forget about it for a month or so
7) Reread and make any necessary changes
8) Send it off.
Now promise you won't share my secrets with anyone else.