The common features used in the measurement 6Li(n,α), 10B(n,αγ), and 235U(n,f) cross sections presented in three subsequent papers are described. The experiments were performed on the 200-m flight path of the National Bureau of Standards Linac and cover the neutron energy region from 5 to 800 keV. The neutron flux monitor was a hydrogen-filled gas proportional counter located at the end of the flight path, while the primary detectors specific to each of the three cross-section measurements were placed 70 m along the flight path. The properties of the neutron source, the detailed operation of the flux monitor, the data acquisition system, and the data analysis procedure are described. The systematic errors in the neutron flux measurement are given.