In a collective action, people act together with the intention of producing public goods. Public, or collective, goods are states or objects that benefit the many but only emerge if a sufficient number of persons make contributions. The present study explains de dynamics of participation in collective action campaigns by considering the interaction of different processes. With the resulting model it is possible to determine the optimal combination of diffusion measures for such a campaign. Before using the model for experimenting, we calibrate its parameters using data from a real world collective action. We find this to be a most important step in order to demonstrate that the model can be grounded empirically and to demonstrate the practical usefulness of simulation for consulting and design of real world processes. Finally, some “what if” scenarios reveal the model’s power of explanation and prediction.