Long post warning 
Ok when I am planning a story I ask myself these questions:
- What genera do you want to write?
- What do I want to write about?
- What characters do I want in it?
- Why is each character important?
- What are somethings that people like in this genre?
- What is something similar to what other stories of this genre have in common
- Is this an original Idea or does it just seem original?
- Is my story to predictable?
If you ask your self those questions you will get the basic info about your story.
After I try to develop the plot into small summary’s:
Exposition
Rising action
Climax
falling action
resolution
And sometimes cliffhanger
this takes me about 1-3 to figure out completely
After that I start to think of what I would like in my story
Example: Full CC, Point system, How advance I want my story.
After that I start to write my story
Often my mind will just run and run with creativity so I just flow through the story.
Tips/Tricks:
Jot down information
Make sure to preview your story for coding errors
Have a close friend view your story and ask for there honest opinion
Make sure spelling is correct
If you are not sure if your story is to long or to short preview it and time your self going through it as if you were the reader.
If you deal with writers block stop writing for a while and enjoy a few days and get back to it (also reading book is a great way to deal with writers block)
This is all I got for you I hope this helps
Good luck on your story 