In today's innovation based competition and with the increase of the innovation pace, the open innovation model (Chesbrough, 2003) appears as a response to the challenges the firms face. Hence, several authors have underlined that mobilizing knowledge external to the firm enhances its innovation ability. Von Hippel (1986) highlighted the role and knowledge of lead-users in innovation processes. Cohen and Levinthal (1990) introduced the notion of absorptive capacity to highlight the role of R&D departments in identifying and assimilating knowledge from the environment. Hargadon and Sutton (1997) showed that some firms that get involved in technology brokering generate innovative solutions thanks to their connections to various technological knowledge networks. If researchers agree to consider that leveraging external knowledge do foster innovation, the processes by which it occurs are complex and understudied. We focus more specifically on the connect phase. How are topics on which to look for external knowledge identified and formalized? How to involve external entities in order to mobilize their knowledge and combine it with the internal one in order to develop new solutions? How to assess the value of various external technical solutions? We propose to formalize four steps and highlight their specificities.