I used to just jump into writing a story without any preparation. If something came up that I needed to take a deeper look at, I'd do it right in the middle of writing the chapter. This did start to create issues when I would spend an hour pouring through screenshots trying to find out how a character's room looks.
That's why now I'm starting to get more organized before writing. The main step that we've taken now is plotting out the chapter before we start writing it. So we'll discuss what happens in the chapter, and I write down a general summary of each scene. Each scene also gets a colored line in front of it, where each color is different for whichever POV we'll be working in for that scene. This way, we know where the chapter is going to begin and end, and who will be the main characters for that particular chapter.
Everything else is still unplanned. Needed screenshots and research happen as we're writing. Fortunately, there's an idea of where the story's going, so the planned chapters don't change (often). Like aeternum, we make use of sticky notes as reminders for changes to edit in or ideas to use in the future.
But I'm going to say that every writer is different. Some writers have everything planned out before they write. Other writers just jump in with only the most basic plot details and nothing else. There's really no clear-cut advice to give that will make the writing process as smooth as possible because writing is art, and art is different things to different people. Also, your story might suddenly change on its own as you're writing it, and the plans that you came up with at the beginning don't hold true anymore.