Existing and emerging liquid crystal devices rely on the development and characterization of new mesogenic materials. Electrical measurements of advanced liquid crystals are an important part of their materials characterization. In particular, the values of the direct current (DC) electrical conductivity determine the suitability of liquid crystal materials for different types of applications. Therefore, a proper evaluation of the DC electrical conductivity of liquid crystals is very important. Even a brief analysis of existing publications can reveal a great variability of the reported values of the DC electrical conductivity for similar mesogenic materials. This apparent ambiguity in the reported results requires a reasonable explanation, and, at the same time, calls for improvements in electrical measurements of liquid crystals. In this presentation, by combining experimental and theoretical results, we discuss how interactions between ions and substrates of a measuring sandwich-type cell can result in time-dependent and cell thickness dependent DC electrical conductivity of molecular liquid crystals. In addition, we analyze the combined effect of the cell thickness and nanoparticle concentration on the values of the DC electrical conductivity of liquid crystals. The presented results can be used to improve electrical measurements of advanced liquid crystal materials.