I’m gonna tell you my process and what works for me and some general stuff! I hope at least some of this works T_T
1 - usually like to start by creating an outline, bullet points, or just the general idea of what I want to write and achieve. For my smut, I usually write a few bullet points of what I want to include, but if it’s something longer I’ll do a full outline. Also i usually write when an idea has come to me, so I’ll write an outline around that and how to get there
2 - something I learned in my creative writing class, is that when you start your story, don’t start suuuper far back. Start as close as you can to the story, if that makes sense. Only include the background you actually need for the story to make sense (doesnt apply if u plan on explaining some backstory later down the line tho)
Third, don’t be afraid to just start writing. A blank page is always scary, but the quickest way to overcome that is to just start. Make it exist first. You can make it perfect later.
4 - i think this is super important, make sure to test your dialogue yourself. If it sounds weird saying out loud and doesn’t naturally flow, it’s gonna be weird to your reader, too. Don’t hesitate to put “like” “uh” or stutters, things of that nature, because it adds realism since humans don’t talk in perfect complete sentences yk (obviously some stuff may not sound natural, but that’s ok too! I would just say make sure this applies for the most part)
5 - use shorter sentences if the scene is fast or intense. Opposite if not
6 - don’t be afraid to add or write throughout the day! I always try to sit and find a dedicated time for writing but it doesn’t always work and if i force myself i can burnout, so ill add things throughout the day little by little
7 - if you’re bored writing it, your readers r probably bored reading it too

IDK IF THIS IS GOOD BUT I HOPE IT HELPS EVEN A LITTLE BIT AND I HOPE YOU WRITE YOUR STORY!!! GOOD LUCK :D