Microwave-based sensing methods have accelerated the advances of nondestructive evaluation in a variety of applications, such as material characterization, structural health monitoring, microfluidics identification, agricultural, and biomedical sensing. Resonance-based microwave planar sensors have demonstrated multiple advantages, including simple fabrication, low-cost, real-time measurements, in addition to nondestructive sensing capability. Depending on the sensing application and properties and conditions of the material of interest, customized sensing methodologies can significantly enhance the performance of the resonance-based planar sensors. This dissertation presents customized, highly sensitive, and nondestructive methods for complex material characterization problems.Resonance-based planar sensors are highly sensitive to the dielectric properties of the materials in their close vicinity. However, the performance of such sensors deteriorates when the dielectric material is attached to a metallic surface. In the first part of this dissertation, a novel nondestructive sensing methodology is constructed for the measurement and characterization of conductor-backed dielectric materials. It permits the characterization of thin conductor-backed dielectric materials with high sensitivity to the dielectric properties. Moreover, the presented methodology constructs a nondestructive technique for different conductor-backed material measurement applications. Another main challenge of using resonance-based planar sensors in material characterization is the nondiscrimination between the intrinsic electromagnetic properties of composite magneto-dielectric materials. In the second part of this dissertation, a resonance-based sensing method for dielectric and magneto-dielectric material characterization, predicated on the fields-confinement approach, is presented. The method demonstrated high sensitivity to both permeability and permittivity of composite magneto-dielectric materials.Differential-based sensing methods have generally been used to enhance the robustness of the measurements by minimizing errors due to the surrounding environmental factors, including the fabrication tolerance and substrate properties of planar resonators. This dissertation takes differential sensing a step further and introduces a novel differential-based sensing method for dielectric and magneto-dielectric material characterization, in the last part of the dissertation. In addition to the enhanced robustness and high sensitivity using the presented differential-based sensing method, it also provides real-time measurements for material characterization and comparison.