I always enjoy looking back at my notes from old writing classes. There's the nostalgia factor, of course, but it can also be quite useful because many of the ideas that I was merely transcribing at the time have much greater meaning to me now. One of the pages to which I often flip my notebook open begins with the line, "Have to earn big scenes." It's an extremely brief way of saying that the "big" scenes in your script -- the scenes that are the most pivotal, and hopefully the most memorable and satisfying -- will fall flat unless you build them up properly via good character work and plotting.
That's one of the most sacred tenets of good screenwriting, and there's little I can add to it (especially since I've covered it in some form many times before). I can, however, use it as a good jumping-off point to another topic -- because the concept of "earning" stuff is actually much more broader and nuanced than the one specific rule I was just talking about. It's actually not a rule at all, but a principle that -- when applied correctly -- can enable you to break all kinds of other rules.
Here's what I'm talking about.
Think about the scene in Raiders of the Lost Ark wherein Indy and Marion climb out of the Well of Souls and race to commandeer a plane before the Nazis take off with the Ark. But not so much the second part; think about the specific moment when they make it out of the Well. Indy shoves a stone out of this rickety little structure thingy, they climb through the hole, and they're back on the road.
Now. Really. Think about it. Indy and Sallah had to dig into the sand for hours upon hours to find the entrance to the Well of Souls... but the exit turns out to be a free-standing, easily accessible stone building a few feet off the beaten path? And in thousands of years, no one else figured that out? That's not just a plot hole; it's a giant sucking vacuum. And yet, no one's ever seemed to care. I'm not even sure that many people have noticed.
Why do you suppose that is? Perhaps because that one improbable moment comes on the heels of the amazing scene in which Indy and Marion are trapped in the Well of Souls with all the snakes. If that's not the most frightening, thrilling, skillfully executed scene in the whole damn movie, it's certainly up there. And it's followed by the great fight scene between Indy and the tough but short-lived Nazi mechanic, which itself ends in a magnificent gasoline explosion. And in the final analysis, those two scenes are good enough that the small but necessary bit of connective tissue between them -- which is clearly a cheat by anyone's definition -- turns out to be not such a big deal.
It wouldn't have worked any other way, though. Imagine if Indy and Sallah had found the Well of Souls by wandering around the desert and bumping into that little stone building. "Hey, maybe this is it. Let's take a look!" Viewers would have checked out right then and there; it wouldn't have mattered how brilliant the ensuing scenes were. But by giving us so much great stuff first, the Raiders script earns its right to cheat a little. So, if we want to get away with bending the rules in our own scripts (and there are inevitably times when we need to), this is the way to go about it.
But earning the audience's goodwill isn't only necessary for papering over iffy plot points. (And really, we should endeavor to do that as little as possible so as to minimize the chance of it backfiring.) Consider a good heist movie like Ocean's 11 or Sneakers. These films require the heroes to perform all sorts of feats that the audience really has no idea how to gauge. Sure, everyone knows that it'd be pretty difficult to break into a super-secure vault underneath the Bellagio -- but virtually nobody in the theater knows exactly how difficult, or specifically what would be required to do it. That's okay, from the writer's perspective, because we don't know how to do it either, nor do we need to. We only need to make it seem plausible. And we do that by earning it.
At a crucial point in Sneakers, Robert Redford's crew needs to get past a door that uses a voiceprint identification system. Only the right person's voice, speaking his own name and a short predetermined sentence, will unlock the door. The solution they devise is fairly ingenious (at least it was in 1992; it's probably been ripped off by at least a dozen other movies by now): they send a female friend on a blind date with the man whose office they're breaking into, and through normal conversation she gets him to say his name and the words in the security sentence, all of which are caught on tape. The crew edits the words into the right order, and voila, they've got their way inside.
Would this really work? Maybe, maybe not. But it doesn't matter. It's incredibly clever, and therefore it earns its own plausbility. That's how things work in the movies. You could have a different solution to the same problem that was, in real life, a lot more accurate (maybe all that's really required is to bang the side of the voicebox a few times) -- and audiences would automatically deem it implausible, because the writer didn't do enough to earn their goodwill.
In Ocean's 11, it's the same thing. Who knows if any of the myriad schemes employed by the star-studded cast would actually be sufficient to penetrate a massive casino security operation? (My guess is that virtually none of them would be, or else Vegas would be a lot poorer.) All that matters is that each of them are clever and interesting enough for the audience to accept their plausibility within the context of the film. This principle works both at the micro- level as each feat is pulled off, and at the macro- level as the film concludes and the audience thinks, "Well, that was pretty impressive; I'll buy that they got away with it." Which means the writer got away with it too.
One final note: Tony Gilroy, current god among writers, toys with this principle self-consciously in one scene of The Bourne Identity. Outside of a hotel where Bourne had stayed prior to his amnesia, he and Marie discuss an almost tediously intricate plan for retrieving the necessary information about his stay. Moments later, as Bourne waits pensively in a nearby phone booth for her signal, Marie comes strolling back with a piece of paper in hand. She tells him she just walked up to the hotel clerk, pretended to be Bourne's assistant, and asked for a copy of his hotel bill. On one level it's a clever reversal of expectations of the type Gilroy is known for; on another, it's a subtle jab at the notion that every single plot point in a thriller needs to be suitably convoluted in order to be plausible.