A manual should make the readers comfortable enough with the machine or object so that the know-how for interacting with the machine is in them, not just in the manual. Effective manuals show readers that the machines are just objects that humans use and control. Your readers can achieve this position if you help them relate to the machine.

Supply context. Help them see the machine from the designer's point of view. What does this machine or this part do, and why, and what kinds of concerns does that function imply? Once readers get the big picture, they will usually try to use the item for its intended purpose.

Explain what the parts do. List all the visible parts and explain what they cause, how to stop or undo what they cause, and what other parts work in sequence with them.

Explain how to perform the sequences. Think of readers as users or doers. What actions will they perform? Think of common ones like turning the machine on and off. Spend time working on the machine so you can tell someone else how to work it.

Use visual logic. One major section should discuss each of the three areas mentioned above. Divide each section into as many subsections as needed. Use heads and white space so readers can find sections and subsections easily. Use clear text and visual aids so readers figure out how to do the actions confidently.

Develop credibility. Give brief introductions that tell the end goal of a series of steps; give warnings before you explain the step; state the results of actions or give clear visual aids so that readers can decide whether they did the right thing.