A general analytical model for the description of phase transformation kinetics, with kinetic parameters that are time and temperature dependent, can be given that exhibits the roles of (i) the nucleation index, a, and (ii) the temperature dependence of site saturation. Recipes for straightforward deduction of the growth exponent, n, and the effective activation energy, Q, have been presented. It has also been shown how the values of the constant activation energies for nucleation and growth, Q (N) and Q (G), can be derived from the dependence of n and Q on time and temperature. The applicability of the kinetic model and of the recipes for isothermally and isochronally conducted phase transformations has been tested by analytical and numerical calculations and by application to the crystallization kinetics of amorphous Zr50Al10Ni40, as measured by means of isochronal differential scanning calorimetry.