The Game Master’s word is law. You can adjust equipment prices, spell effects, task difficulty, monster HP, etc. Just be consistent. Changing the rules too often frustrates players quickly.
Keep play casual. Be fair, but avoid letting “rules lawyering” bog things down; make a decision and move on! Don’t worry too much about making everything balanced and perfect, just keep the game moving!
Traps and Puzzles: How to set obstacles to the players.
Encounter Difficulty: General rule about encounters faced by the players.
Ennemies: Different kinds of ennemies your players may have to fight.
Adventures: Some hints about how to create an adventure.
Sample Quest: A first simple adventure for your players.