“Value co-creation” among actors related to service provision is one of the key concepts in service design. Living Lab (LL) is a co-creative service design methodology in which designers and users collaboratively design services. In LL, users are actively involved in service design processes over long periods. Because LL is a design methodology based on long-term co-creation with users, its practices involve more direct and indirect communication and collaboration with users than typical service design does. Therefore, in order to make value co-creation successful in LL projects, it is crucial for designers to use not only knowledge of service design methods, but also practical know-how related to “facilitating long-term co-creation with users.” Such know-how is not always shared, however, among LL practitioners, because it is often buried in their experiences. Thus, LL practice currently places heavy reliance on the practitioners’ intuition and experience. Therefore, to support LL practitioners, it is essential to extract key know-how on how to achieve successful LL projects from experienced practitioners, and to describe such know-how. This would allow us to share and reuse know-how in planning and running an LL project. Hence, the purpose of this study is to extract such key know-how for LL practice and describe it in an easy-to-reuse manner. We first developed a workshop to extract key know-how for LL practice. In this study, we held the workshop twice and could extract 30 items of key know-how. Subsequently, we described the extracted key know-how as “patterns” by using the pattern language framework, and we developed a booklet listing the 30 patterns in an easy-to-reuse manner. The booklet can be used by LL practitioners to refer to and reuse the key know-how for LL practice. Through an evaluation, we confirmed that the developed booklet is useful for LL practitioners for referring to and using LL know-how.