I usually start with a broad mechanical concept — melee, ranged, healer, or the like. Often that bit is discussed with other players to see what they’re thinking. I don’t want to end up with everyone trying to fit in the same niche on accident.

Then I refine the idea by thinking about flavor. Sometimes I’ll find a picture at this stage, then try to build a character around that. Otherwise, I’ll try to come up with an interesting backstory or bit of the world that we haven’t explored before and build around that.