1. Lack of Preparation
Nothing says “I’m a green GM” more than making the players wait five minutes whilst you try to find the NPC’s stats or work out what happens next. Fortunately this is easy to fix. Read the rules and adventures beforehand. Bookmark key pages and get that highlight pen out.
This may be dull, obvious advice but it is amazing how many new GMs fail to do this. Being a GM involves more work than being a player and this is where 80% of that work should be. As a man on the telly once said “Failing to prepare is preparing to fail”.
2. Me versus Them
If you ever feel vindictive against your players or think “This will show them”, then stop the game right there.
As a GM, the player’s enjoyment of the game is your responsibility, even at the cost of your own enjoyment. To be a good GM you have to be able to swallow your pride and let your carefully prepared dungeon be trashed by the party. If you turn the game into a fight between the players and the GM, everyone loses.
A common mistake by new GMs is to expect the characters to follow the plot. It can be incredibly frustrating when players won’t follow your carefully prepared story-line and there is a temptation to try to force the players into a situation. Making a player do something or having some Deus ex Machina device to achieve your goals is bad GMing and leads to resentment amongst the players.
If you are writing your own adventures, be doubly aware of this danger. Never write an adventure where you expect your players to conveniently surrender to a monster, or to turn up at a particular place and time. The more your plot depends on the players doing a specific action, the greater the chance they won’t do it.
4. It’s Not In The Rules
Newbie GMs often make mistakes when a situation not covered by the rules occurs. Either the GMs decision will be immediately and obviously unfair or having allowed a character to do something once they can repeat the trick and become unfairly powerful.
The secret to minimising these problems is to talk the situation through with the players before you make your call, listen to what they say and then make your decision, remembering to explain your reasons. If the decision subsequently turns out to be a bad call, own up to the mistake and rectify it if possible, even arbitrarily reversing your decision if necessary.
5. Respect My Authority!
Many newbie GMs are afraid of looking weak in front of their players. They seek to stamp their authority on the game by demanding only the party leader talks to the GM or punishing players somehow. Never do this.
Authority comes from respect and respect has to be earned.
A new GM can earn that respect by being prepared, by being fair, by letting the players enjoy the game in their own way and not being afraid of making mistakes. A good GM is a leader who inspires players to follow them, not a dictatorial authority figure who tells them what to do.