First step you need to take before your able to teach a task is determine what the actual content of that task is.
This sounds like an open door, but actually this can be more difficult than that.
You are the learning expert, not the expert on the content and the content expert is not a training specialist. So the trick is to combine the expertise, come to the details of the task and structure this so it can be transferred to the next person. Be aware that the content expert is often not aware of his expertise anymore, since he’s done the task numerous times (unconscious competent) and might underestimate the skills it takes to do the task.

First thing to do is to determine the sequence of operation, the steps that are taken while doing the task. This defines WHAT is done.

Next step is to determine HOW it’s done, by determining what is critical in each step.
Only what is critical (safety, make or break, easier/faster) should be written down, not the nice to know stuff, or what will be obvious during the demonstration part of the training.
This is crucial to distinguish the must-know from nice-to-know.

Finally we document WHY the critical items are indeed critical. We don’t want monkey-see monkey-do behavior we want people to act he right way knowingly, because that will sustain the correct behavior over along period of time.

The task analyses will document what needs to be trained, this does not mean that each and every detail about the task is written down. It enables a efficient and effective training process by focusing on the core without any distractions.