Some things off the top of my head:
I second (or third?, fourth?) the Power Cards. We all made fun of the first guy in our group to bring a set. Now they're pretty much a requirement.
As DM, be sure to know all of the little rules to eliminate checking the book. Study chapter 9 and memorize as much as you can. Things are a lot more simple then they used to be. Except Cover. Don't try to draw lines from assorted corners of squares. Just say +2 to ac and move on.
Feel free to remind the players of the actions they have left, at least for the first couple of turns. Probably not necessary all night. For example, you can remind your dwarves, clerics and dragonborn that Second Wind, Healing Word and Dragonbreath are Minor Actions, respecively.
If you're making up the encounters yourself, be sure to use a good mix of NPC types. (Brutes, Skirmishers, Controllers etc). Throw in some funky terrain, too. The small Kobold Hall adventure in the back of the
DMG is a great little startup adventure. As a DM, I think you'll find that creating encounters is one of the coolest parts of
4E.
Oh, and have fun.
Later!
Gruns
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