Things to consider when writing RPG text: keeping it short, keeping stats short, keeping it all in one place, don't require leafing around, have art that referees can show to player, have maps that referees can annotate

The mini settings I like to generate where the environment or the map generates inspiration for conflict: the river valleys generate political entities, the swamps and mountain peaks religious entities, add secret societies, a long war somewhere else...

Mass combat! That is all.

Keep adding where players go, keep track of the open plots, let alpha players push the campaign, involve quiet players, how to plan with your players, negotiate background, and discover personality

Running the wilderness: one hex is one day on foot without roads, using a different random encounter table for every region, how to find their lair, or their tracks

Creating settlements, starting with a few non-player characters, rumours about adventures to be had nearby, the importance of merchants

Running Dungeons, when to roll for random encounters, how much XP to give for monsters, how to restock dungeons

Keep prep short. Use every idea right away. Be impartial and be adversarial. Let them struggle.

No skills. Fewer classes. Quick and random character generation. Smaller bonuses, little damage, few hit points. Rare healing. Simple combat. Treasure is XP. No magic shops. Random encounters.

No clerics. Healing magic makes fights and delves longer. Undead turning makes fights with undeads easier. None of this makes the game better, but instead the Old Testament references break my immersion.