User instructions, and especially operating instructions, are an essential part of the FDA's "medical device labeling" requirements and are intended to help ensure that the device is used safely and effectively. Their design should go hand-in-hand with the design of the product that they are going to accompany. However, for one reason or another, they are usually treated as something that can be tacked on at the end of the device development process. At this stage, it is often realized that, had the device been designed differently, it would have been easier to instruct the potential users. However, it is generally too late and the instructions have to be formulated around the fixed design of the product. Also, in the clinical engineering environment of healthcare organizations, sometimes there is a requirement to produce tailored operating instructions for certain groups of users (especially patients and carers) in certain circumstances, e.g. when the manufacturer's instructions are inadequate or a device has been configured for a particular type of user group. This paper attempts to demonstrate a practical approach to producing effective operating instructions for a product that is already at the far end of its development process or even marketed.