In much of my funded research, qualitative data about people's experiences 'feeds' a collaborative process of intervention development or service improvement. When all stakeholders are involved in this process, it is often called co-design.
One approach, which provides some helpful formal structure and resources, is Experienced-based Co-Design (EBCD). It was first developed by Glenn Robert.
EBCD includes a suggested structure for bringing together the different perspectives on a problem (and preparing people to collaborate). This helps to manage some of the worries about consensus that can sometimes put people off co-designing (everyone doesn't have to agree on everything), and it also helps facilitators to manage some of the power differentials in a safe and ethical manner (everyone has a right to be heard). This is especially important when adapting EBCD for mental health contexts.
EBCD provides a really useful framework, but reviews of co-design work in mental health show that there is a lot of flexibility in practice about how the principles are applied. This is important, because we often need to find creative ways to engage and involve people with distinctive preferences, and unique prior experiences!
On the iCATs project, we co-designed a pathway for delivering an intervention in schools.