How do you characterize a process for controller tuning?

Process characterization identifies key parameters: process gain (Kp - change in PV per unit change in output), dead time (delay before response begins), and time constant (time to reach 63.2% of final value). Methods: step test (apply output step in manual, record response), pulse test, or relay auto-tune. Calculate process parameters using tangent method or software analysis. These parameters determine whether process is self-regulating or integrating, fast or slow, and guide tuning method selection. Document at multiple operating points for nonlinear processes.