This paper disseminates work from the European Give&Take project, which aims at co-designing service sharing among senior citizens based on a mobile and distributed platform. With this project as a frame, the authors' paper addresses methodological considerations of participation in co-design for ageing. Based on the notions of design culture, communities of everyday practice and situated elderliness the authors present accounts from two European countries, and discuss methodological issues related to mobilizing senior citizens in co-design work as they have manifested themselves and influenced the Give&Take project. Challenges for mobilization are identified, based on an analysis of attitudes and values among design researchers and senior citizens. This analysis lead them to identify and discuss three strategies for mobilizing senior citizens in co-design of mobile technology: 1) Understanding being ‘elderly' as situated elderliness rather than closed categories; 2) Understanding how ad hoc or loosely coupled infrastructures can define a community rather than a formal, organisational structure; and 3) Understanding the nature of mobilization and motivation for participation as processes that continue, and need to be supported, also after completion of the project. These strategies have emerged in the authors' work on mobilization and service sharing, but may apply to a broader context of infrastructuring and ongoing negotiations.