i’m not an expert bc i only just started taking time to plan too but i suggest first thinking of the overall vibe and aesthetic you want and then take inspiration from other forms of media within that same vibe (shows, movies, books, etc.) to help develop the plot. plan out your characters throughly you can find character sheets online. it helps them seem more human. make moodboards and playlists. music helped me come up with a lot of ideas. i also got a lot of ideas from pinterest quotes. and write a few chapters before you publish just so you know what direction you’re going in and you’ll be able to go back and change things easier.