@Mattttttttam i'd recommend doing research on what youre writing about for sure if it has some realistic factors (for example, in my story i need to research about some things about LA) and if you have a favourite author, analyse what you like about their writing and see if you can adapt that into your own story. one story i love to reread is the story 'the sniper' by liam o'flaherty, though its different for anyone (ex. stephen king, rick riordan, harry potter books). id also recommend a thesaurus to avoid repeating words too much in a sentence or paragraph but really really fancy words sometimes just dont work in a situation because of how out of place it looks.
sorry for the long message, but i hope this helps! this may not work for everyone, but this is just what works for me :) gl on writing your storY!