If you are interested in RPG design theory, Monte Cook's Substack newsletter is a good read:
If you love tabletop roleplaying games, you’ve come to the right place. I’ll be writing about games and specifically game design, with an emphasis on what we love about these games and how to best reinforce those aspects in a game.
M.T. Black has compiled their top 50 GM tips onto a single page:
I’ve been collecting Dungeon Master tips for several years and I now have a massive list of them. Following are the best fifty, in no particular order:
As a gift to myself, I had a Voice Actor coaching session to improve my characterization while running. https://erinfitzbadass.com/
I got some great tools to help improve the way I deal with characters and characterization. Definitely recommend.
I don't want to give away too much that feels like part of her special sauce that she teaches. So I'll say this: Finding inspiration for a character by focusing on one particular body part.