Alright, this is a blog bandwagon I'll finally jump on.
Here's my DM advice. A lot of this stuff I've only really learned in the past couple of years. I must also point out that much of this advice I actually learned by being a teacher. Teaching and GMing are frighteningly similar at times, in terms of the thought processes and skill sets you need.
1. Be prepared, but also be prepared to gleefully throw out everything you've prepared and go with something you just thought up that is better. Don't run from it. The stuff you think up off the fly is often some of your best stuff.
2. Energy, energy, energy. If you phone it in, they'll be on their phones (or iPads or reading core books to games you aren't even playing, etc.) You don't have to be a masterful voice actor or spew purple prose descriptions for every place they go, but your excitement should be palpable. I'd also say that you should be out of chair as much, or more, than you are in it.
3. Give 'em choices, and let those choices actually matter. Sometimes they don't want to shatter the Orb of Darkness. Fine. It's your job to deal with that. Maybe they want to pawn it. Maybe they want to keep it. If you want it shattered no matter what, better let NPCs do it and do it off screen, lest the players decide to stop them to save the Orb. This ties in very closely with bit #1, above.