Lew was Contributing Editor to Dragon, White Dwarf, and Space Gamer magazines and contributed monsters to TSR's original Fiend Folio, including the Elemental Princes of Evil, denzelian, and poltergeist. You can follow Lew on his web site and his Udemy course landing page.
Most people know the expression "can't see the forest for the trees," that is, you get lost in details and fail to see the big picture. In game (and level/adventure) design it's usually the big picture that counts, for players. Yet many designers, even experienced designers, sometimes get bogged down in details at the expense of the quality of the game as a whole.
When someone says a game is "fun," you probably don’t really know what they mean, and maybe they don’t, either. Until you recognize that what's fun for you isn't necessarily fun for every game player, you cannot be a good GM.
Back when Dungeons & Dragons was new, the designers and most of the players were wargamers. Typical adventures involved threats to the player character's lives and possessions - their money and magic items. As the hobby has grown, more of the participants are not wargamers, and many campaigns must find other ways to create tension, or abandon tension entirely in favor of linear stories or other means. People refuse to have their painstakingly-crafted characters killed.
If you run a big RPG campaign, with a lot happening other than the adventures of the characters, often there will be a war on. I had to create a list of fundamental patterns of warfare for an online class I'm teaching, and thought the list might benefit GMs.
Role-playing has existed for a century, if not longer. Some role-playing exercises (for education or business) are games with active human opposition, others are puzzles. You play a "role" even in Monopoly, and in many other board games, especially wargames ("you are the commander" said Avalon Hill long before "RPGs" existed). Yet most people would agree that hobby RPGs really got going with Dungeons & Dragons.
"Lifestyle games," games that are hobbies in themselves for players who rarely play anything else, are almost always great games: Diplomacy, Bridge, Chess, Magic: the Gathering, Dungeons & Dragons. But not all great games become lifestyle games. What makes a game "great"? Not good, not a flash-in-the-pan, rather an all-time great game?
There are two different extremes in arranging fights. One is like war and the other is like a sporting event. Sporting events are supposed to be fair contests between roughly equal forces. On the other hand, war is the epitome of unfair competition.
I was reading about the level cap increasing from 60 to 70 in an online game, with many new possibilities/abilities. "How do people keep track of so many abilities at such high levels?" I thought. Then I realized yet another reason why I prefer simple games: "A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away." Antoine de Saint-Exupery. Another version, about Japanese gardening, is "Your garden is not complete until there is nothing else that you can remove."
If you're going to design games, or GM RPGs, it helps to understand a little bit about what makes games enjoyable. Game publishers often say in their guidelines for designers "game must be fun," but I've always found this to be useless because fun means different things to different people.
Why is pure innovation regarded as important in games and adventures, even as it turns out that it hardly ever happens? People like to be surprised when they play games, and some of the most famous game designers such as Shigeru Miyamoto (Mario, Zelda, etc.) look for ways to surprise players. A true innovation is going to be surprising because no one has ever seen it before. On the other hand, even though most "innovations" have been done before, if the players don't know about that then they can be surprised.
An RPG GM has many of the same tasks or duties as a game designer. Even though what I’m saying today can be taken as game design advice, it also applies to the GM as he/she creates an adventure, even as they prepare to run an adventure created by someone else. "A hero ventures forth from the world of common day into a region of supernatural wonder. Fabulous forces are there encountered and a decisive victory is won." Joseph Campbell
In my experience with contemporary college game clubs, there are many younger people who have not yet tried tabletop RPGs. I was also told that many of the players coming to the evening games at a local shop have been new to tabletop RPGs. This is different from my pre-Internet, pre-video gamegeneration (Boomers), where most game-minded people were exposed to D&D because it had so little competition for leisure time.