The approach presented in this overview paper exploits that modal logics can be seen to be fragments of first-order logic and deductive methods can be developed and studied within the framework of first-order resolution. We focus on a class of extended modal logics very similar in spirit to propositional dynamic logic and closely related to description logics. We review and discuss the development of decision procedures for decidable extended modal logics and look at methods for automatically generating models.Published in de Swart, H. C. M. and Orlowska, E. and Schmidt, G. and Roubens, M. (eds), Theory and Applications of Relational Structures as Knowledge Instruments. Springer, 38-67 (2003). Abstract, BiBTeX, PDF.