Before you start writing on a novel or story, its always good to create a writing plan in advance. What’s a writing plan you may ask? Well a writing plan is a plan where you write down all the important stuff you want in the story. So you could start by lining out what characters you want to implement in the story(good guy versus bad guy). Most importantly is of course to make the main character come to life for the reader, so make sure you write down how he or she looks, what his or her perks are, if he/she is sportive or not, stuff like that. You could even write down if the person is married or not, has children or not, or has pets or not. Its all up to you how far you want to add detail to the story, as long as it fits in with the story.
You will also need a setting to put your characters in, so for example you want to write about someone living in San Francisco, or New York. You could then write this down in your writing plan, and add more detail, so where exactly does the main character live, like in what street, or which neighborhood. It could also be, that you want to write about someone living in a totally different universe, so make sure you write down, what the planet looks like, what kind of village, town or city the character lives in, or if the character lives in a forest. Like before, the detail is all up to you.
Conflict is the most important thing of course for a story, so make sure you write down all the conflicts you want in your story. So for example, you want two brothers to fight over something, or two men fighting over a woman, good versus bad, two colleagues fighting over a job, whatever. Just write ti down in your writing plan, so you can check the plan later when you are writing your story.
So as you can see, a writing plan can be very usefull as preperation for your story.
Good luck with the writing!