World building: Ask you questions!
If you give me an overview of the world you're building for a story or a game, I'll help you add details by asking questions about how things work in your world.
In a world much like our own, there's one small change. What are the ripple effects? (Could a world much like our own even have developed if that small change occurred long enough ago?) I'll help you figure out how the world could still look something like ours.
Far in the future, technology has created a where... something important is happening. What kinds of people are showing up in your stories? Why them? What professions could side characters have? I'll help you figure out enough of the back drop that when you need to know, it's there.
Magic works. Mythical creatures are real. You don't want a static quasi-medieval European world (or you'd at least like to explain WHY it's static.) What abilities can people have? Are they studied like the sciences? If there are inequalities in your world, how do they keep the downtrodden folks who have magic under control? (Or is not having magic the way folk become downtrodden in the first place?) What jobs would a mythical-to-us being hold in this world, or do they live separately from humanity?
Training & Qualifications
-- A writer (which means I've done some world building.)
-- A reader (which means I've read stories with worlds that worked... and worlds that really didn't.)
-- A mathematician (which means I've been explicitly taught to poke holes in everything!)