Hobbies And Interests
Prepare
Spend between one and four hours preparing for each session. Have at least the core rulebooks available: the "Player's Handbook", the "Dungeon Master's Guide" and the "Monster Manual." Other books expand upon these three, either directly (such as "Monster Manual 2") or based on a theme ("Heroes of Horror"). There are also pre-published adventures if you do not want to write your own stories. Divide your time between familiarizing yourself with the story, learning the attack powers of the monsters and setting up the board for miniatures if you use them.
Know Your Players
Get to know the players and the stories of their characters. For example, if one player has a love of espionage or mysteries, consider using a Skill Challenge that requires the players to hunt for clues to a murder or robbery. If another player's character has a fear of the undead, a vampire ambush (either as a monster fight or as a Skill Challenge) can give him a chance to be extra heroic (or terrified) and lead to Milestone rewards. Don't focus too much on one player, though.
Enlist The Players
Encourage your players to actively learn how the game works. Start small by encouraging them to be familiar with their character sheets and the terms used in their attack and utility powers (for example, if a power says that it lets you "shift one," the player should know that "shift" means moving your miniature one square in this case.) Invested players can help remind you how different mechanics (such as 4e's new Milestones or Wishlists) work as they come up.
Be Flexible
Make your game sessions flexible so that players can do what they want. If you planned for the story to take place in the haunted castle but the players decide to investigate the dark forest instead, either create a reason for the castle's monsters to also be in the forest, or use a new monster from the Monster Manual, accompanied by a story element that reminds the players of why the castle is important. A slight difficulty that 4e adds to this challenge is the emphasis on groups of monsters instead of single opponents (unless you've planned encounters with Solo and Elite monsters), since groups may be harder to transplant than individuals.