So for a few days prior to actually tackling a script, I’m studying how (for example) Threepio’s head is shaped, and how his joints bend (or don’t), trying different approaches to rendering his shiny finish. This is the research stage. These aren’t drawings that make it into the comic, usually they aren’t even good. They’re notes that help me remember the details that make Threepio recognizable, and not just a generic humanoid robot.
If we’re referencing a game I own, I put it in and play for a little bit. I pause the game, or set characters up in corners and sketch them until a zombie comes along and eats their brains. I look up playthroughs on Youtube and pause the video to sketch environments. The goal is to get familiar with the characters and settings I’m going to be using.