The results of experiments on the study of the processes of step-by-step tuning of parameters by a human-operator are given. It is shown that operators used two tuning tactics to search for global extremum. The first is aimed at finding out the global features of a custom system. To do this, the operator sets several parameter values that are evenly distributed over the entire range. The second tactic is the motion by parameter that tracks the local features of the Quality Score. It is shown that the first tactic is more effective. The features of the parameters adjustment processes are described.