It depends. I'll write a brief for myself when I feel I need to organize the plan/idea better. If its simple or something i'm kinda comfortable with, I can search out refs first or draw something then get reference images(which I like more sometime as to not limit myself to early)
All these characters share a similar staring point of having to wear street clothing. Somewhat hiphop urban vibe. Being able to fight in these clothes is a plus. More on this with more characters. Probably other things I could go into, but, some are project specific and I don't wanna bore with an essay. Maybe a future video if I don't get lazy.