Tabletop role-playing games like Dungeons and Dragons can be really big and complicated. New players can be easily overwhelmed with all the rules and weird terminology.
If you want your friends or family to role-play with you, it is important to be patient and supportive while teaching new players to learn your game.
Creativity and fun are at their best when the whole group works together.
keep it simple

Focus their learning on what is personal to the student. Attacks. abilities, and spells, that are specific to their character.
create a supportive environment

Let new players tell you (the DM) what they want to try, and you can tell them what checks or rolls they will need to do. Instead of overwhelming new players with all the rules, let them experiment in game, and learn as they go.
Let new players be ok with not knowing all the rules. Let them know that it is okay to make mistakes.
Be open and accepting. Don't condescend or make fun of players who don't know what to do.
Allow new players to make mistakes. Do not judge or criticize a noob mistake. Being critical or judgmental automatically kills the learning process.
Don't assume the worst in people or new players.
working with new players

Don't make assumptions about people or their actions without talking to them first. ask them to clarify whatever you are worried about.
Nothing is worse than that person who complains, criticizes, or starts ranting without knowing what is going on. Do not be that guy.
Players and dungeon masters will like you a lot better if you aren't complaining.
Be welcoming

Most tabletop RPGs are big and complicated and it can be overwhelming for new players. Ease the burden by helping out any way that you can.
A lot of players are new to the game, we should never assume that people know everything.
Be welcoming, supportive, and inclusive. A group game doesn't work unless you are actively part of the group. If a new player doesn't feel welcome, they aren't going to want to play at all.
review your house rules before Each session

Remember that every dungeon masters play style is different. Every group has different players and a different group dynamic. No two games are ever the same. So don't expect assumptions or behavior to be exactly the same.
Make sure all players who come and go from your table know your house rules and the consequences for their actions.
This might feel harsh at first, but you'll know it's worth it when there are a lot less arguments about how to calculate critical hit damage.
Behavior expectations should be common knowledge.... Things like waiting for your turn. Or rules like don't be a cheater. It is important to talk about this stuff instead of assuming that everyone knows how to behave.
Dungeons and Dragons is supposed to be fun. The more supportive and relaxed environment you create, the more fun everyone at the table will have.
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