Just been looking back over this classic thread I started on ENW a couple years back - http://www.enworld.org/forum/showthread.php?333786-Pemertonian-Scene-Framing-A-Good-Approach-to-D-amp-D-4e
I found 4e works best with what Ron Edwards called the "Driving with Bangs" approach, or open-resolution scene framing. I found it worked poorly with sandboxing, it is not designed for the world-simulation approach at all. It is also not a good fit for linear railroading because combats take so long, people get easily bored and exhausted (see pretty much every WoTC 4e adventure!). Ideally every 4e combat should be meaningful to the players.
Essentially, 4e works best as a Dramatist game where there is a good deal of player/GM cooperation in campaign direction, but not as a status quo sandbox world-sim, rather as an exercise in dramatic story creation. The 4e DMG2 advice by Robin Laws is good and worth reading, though could perhaps have made this clearer.
4e combat is best done with an eye to both drama and combat-as-sport Gamism; it's the only edition where I'd actually recommend using the encounter-building rules. I don't have a big stack of encounters ready to go - for a session I'll prep 1-3 encounter groups, and some possible encounter areas (ie I'll pack some Paizo & WoTC battlemaps, and maybe think a bit about the terrain) but the actual combat encounter(s) will normally arise in play as a response to player action.
Tools - I use battlemats, minis. I use the old offline monster builder pre-game to help stat up my monsters. I don't bring many books to the game, I'd rather bring more minis.
I generally edit all the monster stats, esp now my PCs are 25th level. I'll cheat a bit, eg I made a super-Balor Solo just by doubling all the stats of the MV elite Balor. Worked very well - killed a PC! :P
One major thing I do is halve all Elite & Solo monster hp, give Minions a Damage Threshold (Level+2, bloodied at half) and give Standard monsters PC-level hp, eg 5xLevel+5+CON for most, 6 for Brutes, 4 for the fragile ones. Even with that the fights easily take 2-3 hours, partly because they are rarely under Party Level+4 these days.