The finite difference time domain (FDTD) formulation for nonuniformly meshed computational space with inhomogeneous lossy dielectrics is presented and discussed. The use of the nonuniform mesh allows for the analysis of practical geometries with modest computer resources. The selection of FDTD parameters in both time and spatial domains, and its influence on the numerical results is also addressed. Comparisons of numerical results with available measured data show good agreement. This FDTD formulation is applied to study the minimization of crosstalk between coupled microstrip lines. Different techniques are investigated to reduce the coupling, such as an air notch, a PEC doping, a PEC cover, and some related combinations. The numerical analysis of this study shows that the best techniques for crosstalk reduction with only one specific cover height and a limited range for the other microstrip line parameters, is obtained by applying the combination of a PEC doping and a PEC cover.