@zefir - if your Chopper's gang is involved in lots of things, then you have some great opportunities to work in other PCs through the NPCs in the gang (which will inherently create PC-NPC-PC triangles).
So for example, say the Chopper's gang is involved in patrolling the marketplace and keeping the trouble there down to a dull roar. But the gang is doing lots of other stuff too, so the Chopper leaves that operation up to one of his lieutenants, whom we'll call Jughead. So Jughead's spending a lot of time in the market, which perhap is right next to the Savvyhead's workspace (or where the Hocus' followers hang out, or whatever). And maybe Jughead has taken a shine to the Savvyhead, and rather than doing what the Chopper has told him to do (police the marketplace) he's spending all his time hanging out with the Savvyhead, mooning over her and generally making a pain in the ass of himself.
This is a little devious because the Chopper's gang (his big piece of character-defining "crap") is involved, which makes him feel important. But he's off-screen and another player gets the limelight. This same trick can be used with the Operator's crew, the Hocus' followers, the Angel's or Savvyhead's clinic/workspace staff, the Hardholder's lieutenants, etc. It also gives you the ability to work additional delicious conflict into your fiction - as trouble erupts in the marketplace and the Chopper is mad at the Savvyhead for "distracting" Jughead from his assigned duty. And the more stuff the Chopper's gang in involved in, the more opportunities for this kind of stuff crop up.
It also gives you opportunities to bring other players on-screen for Chopper-related scenes. Like when the Chopper has to resolve an (inevitable) issue in the marketplace, he does it by first tracking down Jughead - at the Savvyhead's workshop. Boom! Another PC on-screen.
@Arvid - I too have come to really concentrate on scene-centered methods. It's funny, because this is something for which we all have an intrinsic feel, but that is very rarely spelled out explicitly in telling you how to MC a game. Vincent's "don't make your character's lives boring" is fantastic advice, but unless you understand framing, pacing, introducing tension and escalating it to conflict, exposition, dialogue, and juxtaposition like a filmmaker, it's kind of like black magic - as a player you can feel when a GM is doing it right and when they're not, but it's not always easy to say why. It's like the Supreme Court's definition of pornography vs. art - you know it when you see it.
But when I say we all have an intrinsic feel for it, I think much of that feel comes from watching movies and TV shows, and reading books or comics. Good, gripping stories (regardless of medium) take hold of you and don't let go. They keep things moving, and while there may be some exposition it's not central to the story (as that would be more like a documentary).
Of course the problem is that just as different people like different game-play styles, different people like different movie styles. A friend of mine ran a Battlestar:Galactica-themed Solar System hack in which the character creation, plot elements, and scene framing were designed to recreate the feel of a TV show. I thought it was a great concept. Some of the other players were ambivalent and at least one of them found the whole thing frustrating. And I think much of that has to do with what players are looking to get out of the game.