5: Keep encounters open ended
A) An encounter with one solution is bad. I do not write encounters with a solution in mind. I present the problem, and let the players tell me how it will be solved. Remember they are creative too. Use that.
B) Frustrated players are bad. Look back to the Rule of Yes. If your players cannot solve something because you wrote in a single solution they didn’t think of, they get frustrated. This makes the GM look bad.
C) Use any reasonable solution, be open to solutions you didn’t think of. As above, rule of yes and keep an open mind. You have one brain, your players have one each. Use the brains around you to improve the game.
This took me forever to learn. When you think you have created the really clever puzzle that must be solved, you have likely created a bottleneck they cannot get through. Broad strokes please. Yes, you have a unique brain of wondrous power. That is part of the problem. No one else has your brain or your thought processes.
It is considered cheezy to use pop culture references but use them. Anything that you can frame in game that the maximum number of people will understated. Cackling over puzzles that you think are clever beyond words and they will never figure out. Hey, you’re right, they will never figure them out the game will grind to a halt and the fun stops.
Your job here is not to prove to the world how clever you are. The job is to keep the game moving. You win when the players have fun, not when your super dungeon defeats them.
There is one other thing. The player that complains “There is nothing for my character to DO.” (Usually in a whiny tone) Do not slap them, as much as that might satisfy in the moment. Also do not take the bait. It is not your job to engage the character with custom made center of attention items. It’s nice if you can once in a while. Rather you present the problem, it is up to them to use their character’s skills to solve it.
Job One: Keep the game flowing, write to the KISS principle.