The goal of a set of instructions is to enable readers to take charge of the situation and accomplish whatever it is that they need to do.

Introduction

• Tell the end goal of the instructions (or do that in the title).
• Define any terms they might not know; if necessary, explain the level of knowledge you expect.
• List tools they must have or conditions to be aware of.

Body Steps

• Explain one action at a time.
• Tell the readers what they need to know to do the step, including warnings, special conditions, and any "good enough" criteria that allow them to judge whether they have done the step correctly.

Format

• Use clear heads.
• Number each step.
• Provide visuals that are big enough, clear enough, and near enough (usually directly under or next to) the appropriate text.
• Use lots of white space that clearly indicates the main and the subordinate sections.
• Write the goal at the top of the section—so they can skip the rest if they already know how to do that.

Tone

• Be definite. Make each order explicit. If the monitor must be placed on top of the CPU, don't say "should."
• Discover what readers feel is arbitrary by asking them in a field test.