This report reviews the most representative techniques currency available for power systems spinning reserve evaluation. Both deterministic and probabilistic approaches are tackled. A broad range of aspects are considered and organized in a practical methodological taxonomy. The application of the suggested taxonomy is illustrated with the aid of hypothetical systems, the IEEE Reliability Test System, and the Brazilian South/Southeast/Midwest System. Based on the diagnosis resulting from the application of the taxonomy to the methodology currently utilized in Brazil, several aspects in need of improvement are pointed out. As one of the main results attained, it shown that, the current practice of considering the critical risk period as coincident with the critical maintenance period, lacks practical evidence and theoretical support.