This chapter discusses the critical aspects of sample preparation and surface roughness evaluation for micromechanical property tests in cementitious materials. Sample preparation involves cutting, grinding, and polishing to achieve flat and smooth surfaces, with methods evolving to include advanced techniques like focused ion beam (FIB) and vacuum impregnation with epoxy resin to minimize surface artifacts. Surface roughness is typically assessed using atomic force microscopy (AFM) or virtual topographic experiments based on FIB datasets, with root mean square (RMS) roughness being a widely used metric. The influence of surface roughness on nanomechanical tests such as nanoindentation, modulus mapping, PeakForce QNM, and nanoscratch remains a topic of debate, with studies showing varying degrees of sensitivity. Additionally, the impact of moisture content, introduced during sample preparation, on cement hydration and mechanical properties is highlighted. The chapter concludes that careful matching of sample preparation methods with specific testing techniques is essential to ensure accurate and reliable nanomechanical characterization of cementitious materials.