How does your favourite game ease the GM job ?

Pathfinder 2e has a number of things. The prewritten modules are mostly really good OOTB, unlike a lot of D&D modules. Also they have robust encounter building rules which make it easy to balance things correctly as a GM. Magic items have levels which tells you how balanced they are for a group of a certain level. Stuff like that where it's really easy to judge what can and should be included in your game.

Fate has a part when you start the game to make sure the players already know each other. Nip that "I'm a loner why am I even with you guys?" session 2 problem right in the bud. Fate does this with the "Crossing Paths" part of the chargen

CofD has players write aspirations for their character. These are things the players want to see happen. That is not always things the character wants to happen. It could be something like "Get in a high speed car chase." When players actually engage with this, it gives you a direct channel for specific stuff the players want to do. Players gain XP when they hit their aspirations. Of course, in my experience, a lot of players put approximately zero effort into these. I'll say "Write your aspirations and share them during the week so we can think about how to work them in" and I get nothing. I had one player in a game that was really good at this, and every week would show up with fun and executable aspirations. Eventually one of the other players was like "Why is so much of the game about his stuff?" and I was like "Because he's giving me stuff to work with. You haven't given me much, and when I tried to set up the scene for yours last week you didn't engage."

I might be a deeply bitter old man, on further reflection.

Both my favorite systems makes my GMing job easier and they do it in the same way - they give the players responsibility though their character's goals to drive the game forward. And they have explicit rewards helping in this matter.

Ironsworn (a PbtA) is the more direct of these. The characters swears vows and once they are fulfilled they get XP. Starforged, the SciFi version, adds more ways to earn XP through Bonds and Exploration. But we'll stay with the base Ironsworn. The vows are essentially quests but what makes them different from just any random quest is the mechanics surrounding them. First a tracker to measure vow completion is created, then as progress is made it is filled depending on vow difficulty. Now this sounds fairly standard except the only way to mark progress is through triggering moves, primarily the move "Reach a Milestone". Since Ironsworn is a PbtA the moves are player facing, it is the player through their character's actions that triggers them. Second awesome part is those trackers, each being ten segments long. They aren't automatically completed when they are filled instead there is move "Fulfil your vow" that states

When you achieve what you believe to be the fulfillment of your vow, roll the challenge dice and compare to your progress.

That is when the player thinks their character is in a position to have completed their vow they make a roll and see what comes out of it. It lets the player decide if their little work is enough (not much progress marked, high change of complications) or if they should work harder on it. Awesome pacing tool. Ironsworn is also made for GM-less play which gives so may tools to the GM they can almost go on autopilot.

Burning Wheel has an awesome feedback loop called the Artha Cycle. The very short of it is

• Player states their character's beliefs (goals)
• Player have their character try to achieve their beliefs possibly spending Artha (a player-facing currency used to manipulate rolls) to increse chance for success
• Character earns progress in tested skills slowly increasing their proficiency in them
• At regular intervals (often end-of-session) the players earn more Artha for their character's progression on beliefs
• Player states their character's beliefs (goals)

And so it goes on and on. Often all I have to do as a GM is to keep track of the world and put obstacles in the way of the characters, as in challenge their beliefs. With players working the system I often not only get stated what their character's goal is but also what the obstacle is. Then all I have to do is play the world.

Level Up 5e has one of the best monster manuals I've ever read. It's called "Monstrous Menagerie", it's perfectly compatible with 5e even if you don't use the rest of Level Up's rules, and includes things such as Arcana/History/Investigation tables for each monster, encounter builder for monsters with scaling difficulty, expected treasure for the encounter, and much more, and its layout is very intuitive.

I think there are three main ways to make it work:

1. Giving the GM tools to do the job. I remember reading PF2e and thinking, wow, it fills in so many of the gaps I had to improvise on the fly as a DM, and the balancing systems seems to, you know, work. Kevin Crawford's work, especially the ...Without Number series, famously provides so many useful tables guidelines even if you don't use the underlying system itself. Then there are system-neutral resources like the Tome of Adventure Design.
2. Providing clear explanations for how and why the system works the way it does. I know it's a love-it-or-hate-it system, but Burning Wheel is great for this. It's a weird system, and whatever you think of Luke Crane, it's useful to have guidance and explanations for why the rules are the way that they are. Plus the Codex adds even more. I found I really like GM resources that explain the thought process behind running the game. IIRC some of Ben Milton's work does the same, and I like to have a commentary for my own projects.
3. Giving the players meta-narrative agency. Admittedly, this one is extremely subjective. I have mixed feelings about it. I'm absolutely happy to let my players make some decisions for the game, but I found that my group specifically prefers to inhabit a world rather than shape it, and I'm not crazy about that style of play in practice. It feels more like writing a story than playing it out. TO BE EXTRA CLEAR, this is a matter of personal preference. For those who like it, it works fantastic, and the popularity of that kind of game goes to show how it works for a lot of people.

Game Mastering is not just one job and different games handle or overlook the different GM hats in different ways. The Angry GM has a nice way of breaking what is considered the GMs job into:

• Running the game. The actual at the table game. How to narrate, make rulings and describe results. Game systems with easy to adjudicate rules are going to be easier on the GM. In my experience simple systems like PDQ are very easy to run. Player facing mechanics some times also help ease the cognitive load of running the game like Cypher system or Symbaroum. System familiarity plays a huge part here.
• Scenario design. Writing and preparing for the game. Very few games actually explain how to build scenarios appropriate for them in a clear structured way having the GMs mostly on their own. The best resources I've found are the new "So You Want to Be a Game Master" from Justin Alexander and the various books from Kevin Crawford. Complex systems and systems that expect a tight balance between PC and their opposition tend to make this harder.
• Campaign management. Managing the game and its players. Game scheduling and keeping the game running. Resolving conflicts between the players, etc. There are very few resources for a GM on how to do these. Part project management, part event organizer most of the advice for the GM is found in reddit comments and forum threads.

The Angry may have a rambling introduction for each of his articles but he has touched on many of these issues and I've found his game advice invaluable.

Shadowrun has the worst book layout ever, so nobody really understands the rules well enough to stop me just making things up as I please.

With Hackmaster 5. The balance point of play is on health and equipment. This creates a long term dynamic instead of an encounter or "adventuring day" balancing act. Added with penetrating (exploding) dice and thresholds of pain (ToP) this makes even easy combats dangerous. So there is very little pressure on balancing a fight to make a challenge, every fight is dangerous. This is honestly the biggest flaw with GMing D&D 5e and PF2e, because there isn't really a longterm balance point. And giving players a little extra healing (bonus action healing potions) or a night of sleep makes it much harder to challenge them without a TPK. Which is a consequence of the mechanics fighting logic in the game.

Thanks to Hackmaster's longterm framework equipment can be very impactful on play encouraging exploration. And giving a powerful item doesn't create a future problem for me. I can just roll for items and it's fine. I also don't worry about mixed level parties, weak characters or broken abilities.

Hackmaster Monsters are well designed with lots of supporting information that help inform my choices and provide easy answers. Stuff like sleep cycles and spell components are clearly listed.

For WFRP and CoC, the d100 universal resolution system and simplicity of rules makes it very easy to arbitrate. Effectively there are few rules questions.

Cthulhu also follows a particular flow of dread, terror, gore/horror that push the game forward. But it does typically work best with one shots.

I've found that the least inspiring behaviors of players, from my perspective as a DM, are when they hack and slash in combat. Whether it's built into the system, or you brew it on, giving players free skill checks alongside (rather than instead of) their normal combat turns can make things significantly more engaging and rewarding (for both them and the DM).