Increasing global water shortages and rising irrigation costs due to climate change have prompted the development of irrigation scheduling methods that minimize water use and maximize efficiency. Irrigation scheduling is crucial for conserving water, improving crop performance, and ensuring sustainability of irrigated agriculture. It becomes especially sensitive under limited water resources, where water shortages necessitate a refined timing of water application to minimize yield reductions. This chapter reviews various irrigation scheduling methods, contrasting traditional methods, such as water balance and soil moisture-based approaches, with those based on plant responses to water deficits. Plant-based methods, such as dendrometry, fruit gauges, tissue water content sensors, growth, sap flow, and stomatal conductance measurements, are outlined and evaluated. Recent advances, particularly in infrared thermometry and thermography, have also been highlighted. This chapter discusses the suitability of different approaches for specific crops and climatic conditions, their strengths and weaknesses, and their suitability at different spatial and temporal scales. This section also examines the potential of soil- and crop-based planning methods.