Simple guidelines for any Dungeon Master.
1) Maintain Fun – Your first and primary role as DM for both new and veteran players is to make sure everyone is having fun. When they sit at the table, your players are going to be hopeful that the time is well spent. Most will be hopeful they find glory or treasure, some may be hoping they don’t walk away sensing the night was wasted or frustrating. If the players are enjoying RP dialog with the innkeeper, there’s no need to push them along to the dungeon too fast. If the players refuse to speak in-character to your NPCs you can abridge conversations by saying, “You talk to the warden and come to an agreement on how much the payout will be for this bounty.” Player might say “No, bullshit, I wanna use my spell to convince him to give me more money” and you can ask them to RP the dialog or just let them roll a die and consider the result. Ultimately, you want to read the room.
2) “Yes and” – Being a game master is ultimately group improve. You will describe a forest road with a sign that points left or right, and your players will ask to dig through the ground to find China. Narrative railroading can be the only way to force some groups to follow a story, but with careful improvising one can build tracks on the fly. “Yes and” is the first rule of improve, but it doesn’t mean you can’t say “no”. Rather, it is important to keep up momentum. If the group is doing stupid shenanigans and rolling successfully then their rolls should come with some manner of success. If the group is so eager to act like clowns, as frustrated as you may feel for a moment, keep in mind the “maintain fun” rule and play off of it. Maybe looking for treasure in all the wrong places leads to discovering something they shouldn’t have found, like deceptively disguised cursed items or something that can implicate the party in a crime. Your party digs up random holes in the woods only to find a gold crown. That crown belongs to a recently assassinated prince, but boy isn’t it tempting to wear that shiny new hat into town and see what happens.
3) Reward Before Punishment – Honey and vinegar and flies and all that shit. Bad things can happen, but what is most important is still a sense of fun. You should try to keep rewards in mind that will feel better than the worse of failures. Some parties walk away from a game feeling beat up, a player died, warrior lost his arm, and the wizard will never play piano again. If they saved the universe by going through that hell, it feels like a worthwhile sacrifice. If they got 15 gold and saved a villager they’ll never see again it will teach the party to never accept quests from npcs in the future.
4) Know the Rules – This is the last rule. It is very important, but intentionally last. As the rulebook itself states, your job is to interpret and guide the players through this world. If something specific comes up, you need to set a time limit for how long anyone can argue about resolution. If a player wants to jump off a cliff and you say to use an acrobatics check only for another player to argue it should be strength to measure how well they tolerate the landing, make a call and move with it. It might be the wrong call, but reading the rulebook for 10 minutes to come to that conclusion is not worth the time for one dice roll. The more rules you understand off the top of your head the better, but speak with confidence and most players will think you know even more.