This tutorial covers the fundamentals of reactive sputtering for applications. A short introduction in reactive sputtering is given, dealing with the occurrence of hysteresis and ways to control the process. A theoretical description using the Berg model will motivate the understanding of the reactions involved in the coating chamber. Following the basics, different options for process control will be discussed. Especially for processes that drift towards compound mode the risk of arcing is increasing. Ways to control and avoid arcing will be discussed. Different sensors for the process control will be presented and discussed with respect to benefits and limitations of each one. Reactive process control for industrial processes will be addressed. The course will conclude with recent developments.