Process simulation is a powerful analytical method. In light of the increasing interconnection of systems and the rising complexity of processes, it offers significant potential for savings. However, if not applied correctly, the method carries considerable risks. Only through verification and validation to assess the validity of simulation models can meaningful results be achieved. The "V and V" model from the ASIM working group addresses this issue. The authors systematically describe methods and techniques, providing practical guidance that users can apply individually. This is intended for practitioners, educators, and learners.