I like espresso. I've had my current machine about 3 years and it's been excellent, but in the last couple of months it started to play up - the flow rate through the brew head didn't seem as fast and eventually it slowed to a trickle. The noise made by the pump motor sounded different, too.
I read the manual carefully and followed the instructions to clear any airlocks which the manual suggested might be the cause of the problem. It didn't seem to really help so I tried everything else I could think of to clear those pesky airlocks. No real improvement, so I decided to look at the problem more carefully.
Eventually I had an epiphany. Although the flow rate through the brew head was very slow, there was water escaping from the pressure release valve back into the reservoir. With that new information, I was able to solve the problem in about 10 minutes and the machine now works perfectly again. Better, I did it without using any tools or anything that wasn't in the kitchen already. My point is that the problem and the solution weren't covered in the manual.
A proper manual needs to be comprehensive to be useful and that means not just instructions on how to switch the machine on, but helpful in identifying common problems and providing guidance for what can be done. On that basis, most instruction booklets for appliances fail as manuals. Trainer tip for budding manual authors: the phrase no user maintenance possible, is probably not one that you should use unless it is really true.
So how can you write a comprehensive manual? The most obvious approach is to provide the equipment to some would-be users and find out what happens when they try to operate it without any instructions at all. That will provide a very quick insight into how a group of people think and what kind of instructions would help them to get an acceptable outcome.
If you have access to a pool of machines with long working lives then you can also assess what kinds of problems those machines have experienced and provide advice on how people can analyse their problem and carry out simple maintenance.
I'm just off to have an espresso with a full, rich, crema.