In this chapter, an overview of the "tool box" used to characterize lanthanide-based single-molecule magnets (SMMs) is presented. Although the authors have mainly concentrated their contribution on selected SMM examples, most of the techniques are completely general and can be applied to any lanthanide system of interest. As several, excellent tutorial reviews are available on the topic of physical characterization of magnetic molecules and lanthanide ions, the authors have restrained their discussion to encompass more explanatory examples and highlight the lessons learned from the physical characterizations. In particular, the authors focused on the knowledge typically sought by chemists, i.e. the determination of the "anisotropy barrier" and the magnetic exchange couplings.