Today and tomorrow (plot) are interchangeable, depending on your writing style. For me, who my main character is significant in shaping the plot, but I know other writers who let the plot shape the character.
Anyway. We’ve been ruminating. And so now we should have a good stock of ideas and thoughts to get us started. Maybe you even know who your main character is already. If you do, get started fleshing her (him) out. What are their hobbies, their flaws, their dreams? Do they believe what their elders tell them? Do they long to travel? Are they afraid of the dark? There are so many ways to craft your character. Start writing down all the little things about them, their history, so on and so forth. We should all know how to do this, or at least be able to find the resources to help, so have at it and come back tomorrow!
Next time: Choose your plot