Virtual Organizations (VO) represent a new collaboration paradigm in which the participating entities pool resources, services, and information to achieve a common goal. VOs are often created on demand and dynamically evolve over time. One organization identifies a business opportunity and creates a VO to meet it. The collaboration's rules between the VO members are specified in u contract issued by the organization that creates the VO. VO represent an interesting approach for companies to achieve new and profitable business opportunities by being able to dynamically partner with others. Thus, choosing the appropriate VO partners is a crucial aspect. Ensuring trustworthiness of the members is also fundamental for making the best decisions. In this paper, we show how trust negotiation represents an effective means to select the best possible members during different stages in the VO lifecycle. We base our discussion on concrete application scenarios and illustrate the tools created by us that integrate trust negotiation with a VO management toolkit.