As a newbie DM, it’s easy to get caught up in the things that seem important right before you start your campaign. Your maps, your minis, and your epic Tolkien-esque storyline all take up your undivided attention right before your first game. You are so caught up with what’s happening on your side of the screen, that you may be forgetting the most important part of the equation: the adventuring party on the other side of the screen. Remember that these guys are all there to be entertained by you, so you can’t neglect them nor go into the game not knowing who they are or what they are capable of. You need to study the party, learn what they are capable of, and design challenges that will give them a good run for their money.
My suggestion to you is that if your guys are using the character builder to make their characters, they send you either the character builder file of their pc, or a PDF of the character sheet a night or two before your first session. Have them download a program called CutePDF, which installs on the pc as a virtual printer, allowing them to “print” directly to PDF. This way, you have the characters available to you at a glance via email, and you can begin customizing encounters based on their abilities.
If you have a Rogue in your party for example, make sure you provide something in the adventure to make him feel essential. Locks, traps, a pickpocketing skill challenge to find a set of keys, anything made just for him. Do the same with your arcane characters, who are always going to want to roll their arcana checks everywhere they go, so make sure every now and then that roll actually provides the party with something useful. Players want to feel like they are contributing to the successes of the group, and its partially your responsibility to provide that feeling. Don’t be afraid to toss in a few xp points whenever a character conquers a specific challenge you’ve laid out for him, he’ll appreciate the challenge even more and feel good about his character.
It may be a good idea to sit down with each individual player to get a sense of what type of character they want to be. Does Gentir want to be the typical rogue, sneaking around and opening traps, or is he more of a swashbuckler Han Solo-ish type? These conversations are good to have because now you know that the “rogue” in your party isn’t all that interested in playing his guy like a thief, at least not flavor-wise. You can then create situations that’ll fit his character concept better.
And finally, another good thing to keep in mind as you are starting out in the lower levels is to let your players show off their shiny new abilities they’ve earned for themselves as they gain experience. Players love it when they can use their newest tricks, so make sure you provide a way to get them into the story. Nothing frustrates a player more than to have a particular skill or ability that never comes up in the game.
Remember, D&D is a collaborative game, and by keeping your players engaged, everyone has fun.