The practices normally used in classical digital programs for oscillation mode analysis in dynamically unstable multimachine systems, do not use, in such way a general methodology that allows identification, without a great deal of trial and error, wich machines, are more effectives in providing damping to the system through suplementary signal application in excitation controls. This work attempts to describe methods for application of analysis based on tests that can be easily executed whith classical digital programs. Also a method based on eigenvalues and eigenvectores sensitivity analysis is presented. This method uses eigenvectors to find the groups of coherent machines. To give insight into the relationships between a give machine damping and the particurlar frequency of oscilation, the eigenvalue analysis is used. Techniques for speed stabilizers adjustments are shown to provide performance over a wide range of systems conditions.