The application of quantum mechanics/molecular mechanics (QM/MM) methods in transition metal chemistry is growing steadily. It becomes therefore appropriate to assess the importance of a number of technical issues associated to their implementation. This work presents the discussion of several of these issues, including the eventual need for conformational searches, the choice of the MM force field and the possibility of its tuning. The examples presented here prove that a proper handling of these technical aspects can lead to an improvement in the efficiency and quality of QM/MM calculations.