When working on sound design, one of the first things I do is to hone down the vibe of the game. Sometimes that means an image collage, sometimes it means a list of references to other media, and sometimes it just means a long rambly paragraph, but, before I start creating any sounds, I want to make sure that everything I make will be cohesive and share the vision that the team has for the game. After I have that pinned down, it's just a process of drafting the sounds and creating a soundscape that all ties in to each other and really feels like it comes from the same world.