I sort of do this regularly. I and one of my players have been swapping campaigns every few sessions, so I have plenty of prep time. I bought Dungeon Tiles and minis in bulk a while back, so I have plenty of things to whack. If I want, I can design encounters for PCs with any of the monsters I've got.
That said, if it was just for one solid weekend...
1) Encounters: I'd build up some interesting tactical options, and have them be really challenging fights. Several Solo monsters, at least one dragon, with weird rooms. However, I've also found that random encounters the PCs don't expect have challenged me as a player. Recently we got tricked by the old gelatinous cube, and my Barbarian kept getting sucked back in! Like, every round he got out, then got pulled back in. heh.
After I decide the mechanics, I'd be able to back it up with story reasons.
The combat mechanics are the strategic part; I want to prep the number crunching. I'd also want the prepared encounters to be made in a way that I could drop them in no matter what the PCs do. For example, I'd want the Quest for the Holy Grail to get to the Canyon of the Crescent Moon dungeon. The traps, the monsters, the riddles and puzzles; all of these I'd figure out beforehand. The PCs (Indiana Jones and his dad) can get there however they want, but when they get there I can just pull out ready-made puzzles and run them.
2) Mats & Minis: making everything look intentional is good. Granted, I try for this when possible. It fits witht he above, tho, as I bought the City of Peril set, and dungeon tiles with the Dungeon Delves 4e books, right? I want the PCs to think that everything is supposed to be the way it looks.
3) NPC roleplaying: This is a form of combat, in terms of skill challenges. However, I'm not as sure the PCs will do these as I am that they'll find the map to the Deadly Delve and go for the Mighty Sword of Slaying.
That said, I decide what NPCs I'll need to move the plot to the next encounter, and what they'll want to say or do generally to get the players to want to go there. Apparently I'm good at this when I prep, as my players think it's all them. Seriously.
Otherwise, I'd try to think of what would be fun, and how to accomplish it. This is a regular thing.
But I have no idea how much material we'd get through in 48 hours of solid gaming.
Y'know, if it's 48 hours of solid gaming, I'd likely be able to do a bunch of dungeons. Consider that a good room can be 1-2 hours to finish, with my group at least, with a few spurts of "ok, we finished three in 10 minutes", we could do a heck of a job with a pile of rooms.
How fast do your groups go through rooms?
