Regarding DMing 4e:
Read the DMG. Read the other books too, for rules, but especially read the DMG, because that has more good advice on DMing than you'll find here.

On the Unified Setting:
Be aware that the races for the Unified Setting don't really have good 4e stats. If you want to work through them and get that fixed it should be relatively easy to revive interest, though. The current development thread is here:
>>>/tg/20

Bob 2012/10/29(Mon)22:41 No. 22713 ID: 6a1ec2
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Plan scenarios, but not a hard order to them. If the players fail to enter the room with the dragon, for example, don't force them in there, and don't discard your ideas. Just save the dragon for another room.

When the players try to second guess you at every step (and they will) give them a few red herrings, things that seem important, but are in fact just distractions.

Once you get their guard down with those, then you can provide a minor detail that doesn't seem important, but turns out to be incredibly important. A feather in the old sailor's boot for instance.

Once you really fool them badly, they will try to second guess you from then on even worse. That's when you introduce secretly timed puzzles. For example when they carefully explore the dungeon without missing anything, they return to the surface to find the village has been sacked while they were checking for traps the third time.

That's your basic starting game. After that, like chess, there's no right way to do things. Mix up the above three or do something else entirely. You'll just have communicated to your players that proper balance of trust and paranoia that will hopefully get them really into it.

of course, don't make the bad things too bad at first otherwise they will think you are just fucking with them and not being serious about it.