(1) Create a list of definitions (see below) in a format easy to edit and expand.
(2) Optional: Brainstorm and describe an object critical to the plot. Add to definitions list.

In your definitions list, you'll flesh out details that you'll want to remember later for consistency. You won't have to dig through pages of scribbled notes to find whatever you decided about these definitions - they will all be compiled into a neat list / binder / database / note cards / whatever your favorite form of organization happens to be.

I didn't copy the examples but you can look them up. For Fantasy what are the rules of magic? For Crime/Mystery what are the laws to abide by? And for Sci-Fi how does science come into play? Speculative fiction could have Sci-Fi and Fantasy together.

Definitions define your setting. What are the characters dealing with as they traverse their journey? This is intended to explore what's going on in your world and to create consistency. If you have a lot then at least log in 15 minutes. My world deals with science mixed in with a magical world. So the aliens have learned magic too. But magic affects the robots ruling the world and the MC is a robot too. With feelings due to magic cast on it. The flaws have yet to be discovered, but since the hit the MC is flawed and unable to do its duty perfectly as the aliens in outer space expect it to do. So there's a conflict between what it does and what it wants to do.