Image from Giphy.com. Shot of Sadao Maou in the break room, from The Devil is a Part-Timer!.
Optional: Give Them a Job
Similar to the previous step, and often replaced by Step 6, this is an optional step that is here for characters who are defined by their job first and foremost, and write them accordingly. If this is not relevant, skip to Step 3.
Is your hero a grill cook? How about making your bystander a superhero? What if the pawn of destiny runs a brothel?
Make it interesting, and use common sense on what would work in your story.