I don't have as much experience with Dungeons and Dragons as I'd like. My parents were pretty conservative and skeptical of the whole "magic" thing. As an adult I've gained a little bit of exposure but we've focused more on tabletop games than RPGs (Role-playing games). Still I've played a few scenarios of D&D like the Rick and Morty and Star Wars: Edge of the Empire versions and have a few "golden" rules for being a DM and/or gaming in general.
1. People Matter More Than Games
Games are great and it's really fun to get invested in your stories and characters however that should never overshadow the real people you're sharing the table with. No one should ever have to swallow discomfort or compromise their feelings for the sake of a game. Always remember to treat sensitive subjects with care, check in with your group as you play, and be willing to stop the game and have a conversation if people seem uncomfortable. Remember that this also extends to yourself. No one at the table is more in touch with your feelings than you! You are your own best ally when it comes to caring for your well being.
2. Fun Matters More Than Rules
RPGs are a truly infinite canvas where anything is possible within the realm of your imagination, which means that the rules of a game can occasionally be a limitation. Ideally the rules funnel your creativity, enforce themes, and provide interesting challenges. However, a designer can't anticipate every situation for every group. Sometimes the most obviously fun things for everyone at the table goes beyond or counter to the rules of the game.
RPGs are less rigid than most other games because they are so intimately controlled by the players so they can accommodate bending or even breaking rules in the name of fun. This sort of decision works best if its acknowledged and discussed in the open. Breaking rules and not telling anyone is cheating. Breaking rules as part of a group is working together to have fun.
Generally speaking, if you and your fellow players think something is fun, you should do it!
3. Make Choice Important
The final rule is a twist on an old improve classic. If you know anything about improv, there is a good chance you've heard of the rule, "yes, and". Essentially "yes and" is the basic cornerstone of collaboration. It's about embracing the ideas of the people you are working with then building on them.
Also saying yes to an idea doesn't necessarily mean saying yes in character. Saying yes just means accepting the proposed new reality.
I prefer a twist on this rule: Make choice important. This rule challenges you to look at and build on the idea of your fellow players in a specific way. First, it calls you to view everything that happens at the table as intentional choice that people are making. That assumes intention behind their ideas. Then it asks you to add to those ideas in a way that honors them and gives them personal significance by "making choice important".
At the end of the day "yes and" and "make choice important" are the same thing. Every time you "make choice important" you are also following "yes and". The difference is with "yes and" not every act of building really engages meaningfully with the ideas people have already presented. There are plenty of ways to say "yes and that idea doesn't really interest me". Which is why challenging yourself to "make choice important" will lead to a stronger and more fulfilling game.