This publication explains two rules related to the Ziegler-Nichols methods.The first method described is applicable if the controller tuning is done in a closed feedback control loop, while the second method can be utilized where an open loop step response is available or can be measured. Both tuning rules result in a closed control loop giving an overshooting response with a quarter wave decay of the oscillating control variable. Matlab examples are presented in order to simplify the reader's understanding of the given theory.