In the emergent domain of multi-enterprise applications, existing process modelling approaches need some accomodations. Enterprises involved in such applications require privacy and autonomy considerations. It is of first importance that the know-how of each partner is preserved as much as possible : their competitiveness depends on it. Based on some practical experiments in different domains, this paper discusse some pragmatic process modelling guidelines. Each guideline is explained and illustrated thanks to an example issued from the software process domain. A relationship between this work on process modelling and current research on flexible workflow models and enginers is briefly discussed.