When you want the human/user/customer to be in the center of your process you need to include him during the different stages. This is what co-creative design is all about. It is a necessity in Service Design, as a service always concerns many different people but it can totally be used in product and interaction design.
Design shouldn't be just between the designer and the users. It should include all the people associated, all the Stakeholders. So before organizing co-creative workshops, you need a clear Stakeholders map.
Then you can create 1 or several teams including each of the stakeholders and designers (or at least some of them if you have more than one team). Plan when you will gather the team(s) during your development process: during the research phase you will be able to learn from everyone, during the ideation and evaluation phases the stakeholders will help you create concepts that will fit properly to everyone.
Regarding the organisation of a co-creative workshop you will need facilitators, a lot of post-its, pens, papers, cardboards, maybe clay and you will have to prepare! It can last half a day, a few hours or a whole day so plan the things properly.
1. Before starting to work in teams, it's always good to gather everyone, sums up the project, the information, the objectives, explain the rules (Brainstorming rules for example), let everyone present themselves and use a method to open minds (everyone has the capacity to design!). 2. The work can beginning: use brainstorming, braindrawing, prototyping, card sorting... Facilitators should keep an eye on the time, let everyone speak and document everything (take photos, notes, keep the post-its...). 3. When the time dedicated to one activity is up, discuss the ideas, cluster them all together. 4. Don't forget to do some breaks, have a coffee. 5. At the end of the workshop, gather everyone and discuss the conclusions, the ideas that poped up or any topic one of the stakeholders want to talk about.