Where do things need to be before the chaos begins?

That line is taken from Tempo. Let's look at the heart of this by reading the ending: 

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Thinking in Terms of Positioning and Melee

It can be really hard to switch your thinking from planning-based to positioning based.

Planning is  based on straining to forecast and anticipate actual actions. The driving question is What needs to be done?

 [My list needs to be able to handle one AV14 threat, three AV13 hulls, two units of AP2 armour yet have six scoring units with at least four of them wrapped in an armour transport to make them more survivable for example.]

Positioning is based on spotting advantages. The driving question is Where do things need to be before the chaos begins?

[Stelek's 5th Edition Daemon deployment defense would be a great example of having a plan and adopting it to the circumstances. He has the plan already, but it is because he is playing Daemons that he can use it. He then makes note of the terrain to provide traps for deep striking daemons and keeping them away from his critical units.]

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To plan, you start by identifying critical logical dependencies between necessary actions and time constraints. You plan by making commitments around those things.

To position, you start by identifying critical likely patterns of information flow after tempo epoch shifts. You position by identifying likely islands of calm in the forthcoming information churn. Think about surveying a flood plain that you know will start filling up with swirling waters and howling winds soon. Where are the relatively safe places? What can you do to prepare in those places?

[A lot of Internet opinion is that your battle fortunes are dependent upon your deployment. For Blood Angels players, we need to think about also our reserves and redeploying because of our greater speed than other marine armies. What look like nice places to drop in an Assault Squad or drive your Vindicator 12" onto the board and fire that large blast template. This also means delivering those Assault Terminators into the path of the enemy or force them into a firing lane.]

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Preparing for a melee though, is more like training for a sport by raising general fitness levels as high as you can.