From looking at all the advice I think you guys have covered everything....except one thing I note that everyone missed.....and its probably the most important thing of all....
Make the campaign setting
rich. What I mean by this is put in history behind everything that you create in the world. There should be nothing in a DM's campaign setting that does not have a history or story behind it.
Create that huge battle that occurred in the past that affected the entire realm...then separate every single little town, place, ruin, npc, temple, road, lake etc and give each of these history...maybe life after the Great Battle has forever changed....maybe it hasn't...but what ever you do have something prepared and if you don't write down what you advise to the PC's when you "wing it"....this is very very important for making the campaign world "rich". Names, events and history is what triggers memories with the players and therefore creating the sense that their characters belong. This is vital for keeping them enthralled and engrossed in the adventure.
When it comes time to have a rest and let another one from your group DM
do not stop writing ideas down and creating your campaign world. There are so many things in every day life that can give rise to ideas. Write these ideas down, on restaurant napkins, on word during lunch breaks at work, in between TV shows etc. Just basically keep the ideas coming...some of my best ideas have come to me during odd times....so just keep those "creative juices" flowing.
Most important thing is that the DM is the story teller and the sole person for triggering the players imagination. As soon as you lose sight of this Dungeons and Dragons becomes just a game of chance and you might as well go and play Yahtze...
Have fun and Good luck.
