How to Play D&D
Very often I see people asking for advice when they want to play Dungeons and Dragons for the first time. The advice that I see many people give to these questions is great, but I think that often people forget to explain the most simplistic information because they assume that people already know this information. Because of this, I answer requests for advice to new players and new DMs with the following information. I know that it is very simple and most people will know this. This information is written for the poeple that come into the hobby with no information at all.
Step 1: Dungeon Master Sets the Scene
The DM, or Dungeon Master, tells the players where their characters are and what is happing around them. As a DM, try to describe some information for at least 3 of the 5 senses. What they see, hear, smell, feel, and taste. The first 4 of these will be used most frequently. The DM will have either their own notes of a world they created themselves, or more often, will be using information from a published book that contains a pre-written adventure called a module. After setting the scene, the DM asks the players what they would like their characters to do.
Step 2: The players interact
The players now can talk with each other and discuss possible actions they would like to take. Some players use voices to differentiate when their character is talking from when they are talking out of character. Other players may talk about their character in 3rd person instead of voicing the character directly. Whatever a player is comfortable with should be fine.
Step 3: The Players Act
Players will decide on a course of action and tell the DM what they want to do. If multiple people want to do different things, then the DM will need to decide who gets to act first. You can decide this any way that seems fair. The typical method for this is by rolling initiative, which is rolling a 20-sided die, adding the character's dexterity to it, and whoever has the highest goes first. The players may choose any course of action that they can imagine their characters doing. It is up to the DM to decide if those actions are impossible, difficult, or easy. Once a player has decided what they want to do, they can attempt that difficult action by rolling a 20-sided die. Low numbers will result in a failure. High numbers will result in a success. There are many ways to determine what number is needed for a success. This number is called a Difficulty Class or DC number. If you are unsure of what the DC should be for an action, you can just use 15 for most things until you get more comfortable deciding how hard or easy things need to be. If the DM thinks it's easy for the player to do the desired action, then no roll is necessary, the player just does that. If an action is impossible, the player chooses something else.
Step 4: The DM resolves the actions.
After a player rolls to attempt an action, the DM will describe the results of their success or failure. Then the DM resolves the actions of the other players in the same fashion until all the players have had a chance to do something. The DM will describe what other non-player characters do as when as the environment around the party. They are in complete control of the entire world other than the player's characters. They decide what the weather is like, how NPCs act, how the stars move in the sky, when crickets chirp, and everything inbetween. The DM has unlimited power and can make anything happen in the game. This responsibility is important, because if the DM acts like a jerk, it can cause serious problems. So DMs need to be very careful.
Step 5: The DM Sets a New Scene
After all players have had an opportunity to act, the DM will again describe what is happening now that those action have taken place. The DM will make NPCs speak or react to the action and take actions of their own. The environment may change or interact with the players in some way. Enemy monsters will make attacks against the players. Traps might be triggered. The DM may require the players to make rolls to avoid traps. These are called "saving throws" and use the same dice mechanics as a normal action. The player rolls a 20 sided dice and if they get a high enough number they avoid the trap or take less damage from it.
Step 6: Repeat forever
You can not 'win' D&D. It is a cooperative storytelling improv game. The point of the game is to have fun while telling a story. The only 1 rule that you absolutely have to follow is this: Everyone should have a good time, enjoy the game, and feel respected and safe before, during, and after the game. To this end, it is important that you have a gaming session before you begin playing, called a Session Zero. During this session, you should discuss what type of game everyone wants to play, what themes they are comfortable with, what themes are completely off-limits, and what responsibilities each person in the group is willing to take on in order to help the group have a positive gaming experience. There are many good guides for a Session Zero checklist. In addition to a Session Zero, it is important for a DM to regularly confirm with the Players they everyone is having fun. Sometimes it might be necessary to change the style of game or address potential areas of conflict. Remember, no D&D is better than Bad D&D.