This chapter reflects on some of the lessons that we have learnt over the last few years exploring the design of assistive technology for people with dementia. The key message is the importance of involving people with dementia and their carers in the design process. Such user engagement is crucial in order to highlight their needs, and to guide the design and development process to ensure effective equipment evolves. The chapter discusses some of the issues that arise when working with people with dementia in this way. It goes on to show how the engineering design process needs to be adapted, both to ensure effective designs, and to ensure that user engagement doesn't lead to ethical problems. The chapter also considers specific design techniques which have been found to be very useful such as Wizard-of-Oz testing, the use of carer emulation, as well as techniques that can help the design of devices that are very intuitive to operate. The impact of emotional memory on design solutions, and the desire to empower users through the use of technology, are also both discussed. Several examples from our own work are provided to illustrate all these discussions. The chapter concludes with an encouragement to other designers, that their skills have an important role to play in assisting people with dementia.