In the computer simulation method (NVE ensemble) of determining the properties of classical liquids there are well established procedures for determining the properties of the liquid. We suggest an alternative procedure, for many properties, based on counting the passage of particles through a notional plane in the liquid. This method is used in homogeneous liquids as an alternative way of determining the temperature, the diffusion coefficient and the velocity autocorrelation function. In inhomogeneous systems the new procedure is used to determine the density profile. For all properties, except the velocity autocorrelation function, the method proposed is more accurate for given computational effort than the conventional one.