Ask HN: What steps do you take before starting to write code?

"Weeks of coding can save you hours of planning." For all but the most trivial tasks, some steps must be taken before firing up the old text editor and typing in declarations, statements, and expressions. At the very least, a moment must be taken to fix in your mind the specific problem you want to solve and how you intend to solve it. At most, large projects may require months of up-front specification and planning (though there is much disagreement about how much is too much, and where the point of diminishing returns lies).

This question aims at the midpoint between the trivial and the gargantuan, at tasks that demand more than a simple script but less than a large development team. It also aims especially at work in lower-level languages such as C, because they usually require more careful design before coding begins, but thoughts on other languages and environments are also welcome.

So: What do you do before you start to code? Do you write down a problem statement and design sketch in your native language? Do you make diagrams, on paper or onscreen? How do you know when it's time to start coding? What "pre-coding" tips can you share from your own experience that make the programming phase faster, better, and more fun?