1 What is a model?.- 1.1 The concept of models.- 1.2 Word models.- 1.3 Definition of model.- 1.4 Examples.- 2 Why do I need a model?.- 2.1 Reason for use of models.- 2.2 Complexity.- 2.3 Integration and testing of compatibility of information already collected about a system.- 2.4 Simulation as a synthesis of available information.- 3 How do I start?.- 3.1 Defining the problem.- 3.2 Word models.- 3.3 Diagrams.- 4 What help can I expect from mathematics?.- 4.1 Mathematical notations.- 4.2 Families of mathematical models.- 5 Do I need a computer?.- 5.1 Access to computers.- 5.2 Computer languages.- 5.3 Using the computer.- 6 How do I know when to stop?.- 6.1 Re-examination of objectives.- 6.2 Sensitivity analysis.- 6.3 Verification.- 6.4 Validation.- Appendix: Modelling checklist.- References.