A study of ferroelectric switching is performed experimentally (macroscopically and at nanoscale) and theoretically, within the framework of a lattice model based on the Gibbs-Landau-Devonshire theory. Assuming that the polarization reversal is triggered by latent nuclei sites interacting with neighboring ferroelectric units, we have simulated switching curves and hysteresis loops in the total and partial switching regime. The model parameters have been varied in order to account for the hysteresis loops of PZT samples. Negative susceptibility regions of minor loops are caused by domain inertia in a sample with a lower defect density. The linear dielectric constant calculated from this model exhibits a typical butterfly-shaped hysteresis loop, with peaks in the zero-polarization state, while the second order nonlinear dielectric constant changes its sign in line with the average polarization. The local-integral relationships of the switching process are discussed in the framework of the model, providing useful guidelines for disclosing subtle ferroelectric peculiarities from experimental data.