(Note: I can't take credit for coming up with this "rule." I've seen it before, though I can't think where, or I would credit the source. Possibly on TV Tropes somewhere?)
The inverse relationship between how successful a plan will be and how much readers should know about it beforehand makes a lot of sense. If the plan is going to fail, you want it explained first so that readers will see it failing. They'll understand what's going on, and they'll want to read on as they anticipate the trouble this will mean for the architects of this failed strategy. If, on the other hand, the plan is going to work - well, in a movie, you might have the team leader say, "Listen, here's what we're going to do . . ." and then CUT AWAY, straight to the plan's implementation. Either that, or the person who comes up with the scheme doesn't share it with anyone in the first place. The reasoning here, as I see it, is twofold: you want to avoid repetition, and you don't want to steal the thunder from the actual events when the strategy is put into action.
Basically, you want to avoid either of the following situations:
- Someone explains, either to other characters or to the reader via the description of her thought process, that she is going to borrow her sister's car, rob a bank, drive to Vegas, bribe a bunch of Elvis impersonators to create a distraction, and kidnap a white lion. She then borrows her sister's car, robs a bank, drives to Vegas, bribes a bunch of Elvis impersonators to create a distraction, and kidnaps a white lion.
- Someone is planning to borrow her sister's car, rob a bank, drive to Vegas, bribe a bunch of Elvis impersonators to create a distraction, and kidnap a white lion, but never informs the reader, so the reader doesn't see the significance of the situation when her sister's car won't start.
(Of course, this all assumes that the strategizing party is either the POV character or someone who would communicate her scheme to the POV character. We don't get to be privy to everyone's plans all the time.)
This can, of course, lead to a funny meta situation when you're reading or watching a movie and someone starts laying out a detailed plan. You can assume with some confidence that things are not going to shake out that way.
Exceptions? Thoughts? Diabolical schemes?