Characterizing the spatial variability of soil salinity is an important spatial property that provides crucial information for crop and irrigation management strategies, particularly for site-specific management purposes. Apparent soil electrical conductivity (ECa) is a quick, reliable measurement that has been proven to be well suited for mapping soil salinity at field scale. It is the objective of this paper to present protocols for conducting an ECa survey to map the spatial variability of soil salinity. The protocols are comprised of seven general steps, which focus on the use of intensive geospatial ECa survey data to direct soil sampling that spatially characterizes the 3-dimensional distribution of soil salinity at field scale. A case study is presented to demonstrate the utility of ECa-directed sampling approach. Using electromagnetic induction (EMI) data conducted in accordance with outlined protocols, a response-surface sampling design identified sample sites for a 32.4-ha field in California's San Joaquin Valley (SJV) where soil-core samples were taken at 0.3-m increments to a depth of 1.2 m. The field mean salinity could be established in as few as 12 sites. From the sample design a detailed soil salinity map was prepared of salinity conditions existing in 2002. Analysis characterized the soil as varying from 4.83 to 45.3 dS/m with complex spatial patterns reflecting hydropedology and past and current uses. Spatial trends showed high areas of salinity located in the center of the southern half of the study area. The developed ECa-directed sampling protocols provide the guidelines to assure accurate, reliability maps of soil salinity with far less labor than grid sampling.