atanakar
Hero
This is pretty much how I always start campaigns. Not so much the band of orcs, but the "something is happening, right now" thing. Literally--start of the first session, draw a map and have the players put their characters on it. A little scene-setting, then [stuff] hits the fan.
I started a game of Cyberpunk Savage World with characters drinking in a shady bar in a even shadier part of town. Suddenly a white van turns the corner followed by a pimped car. Guns shots are fired. The van hits the brink wall. Both parties start a shooting war. Seconds later everyone is dead. The PC come out to investigate and find a big stash of drugs in the van. I then said what do you do? Well, they took the drug and ran with it.