Guidelines for prehospital emergency care within the chain of rescue are recommended. At the scene, information about the patient and therapeutical tools are limited. Accidents and emergencies happen outside of hospitals and doctor's offices, while environmental factors and logistic problems strongly determine the rescue process. The sequence of interventions or the choice of the right hospital with specific triage criterias are only examples for these problems. There is only limited scientific evidence for therapies performed prehospitally. However, scientific material for the preparation of guidelines should be evaluated by using standardized criteria. The rules of evidence based medicine according to Cook are a practical way to evaluate and classify scientific material and to establish practical guidelines. In this paper, an 8-step-program is introduced to develop practical guidelines for the Emergency Medical Services Cologne.