Great thread! I wish I knew of this forum when I started last year. My first piece of advice would be to establish a relationship with the other den leaders in your pack....especially those of older dens than yours. They have been there, done that. Learn from their mistakes and then pass your own lessons to the guy coming up behind you.
Get to know the parents. Find out their strengths and talents, and get them involved immediately. Not all will want to be up in front of the group, but they can help in some capacity.
Don't be too proud to scrap a meeting plan. Sometimes the best laid plans give the worst results. If the boys are bored or restless there's no shame in breaking out and just playing a game.
Get outside! Its been said already, but most people hear "scouts" and think camping, fishing, hiking....not craft time.