  Schrieffer-Wolff transformation is extensively used in quantum many-body
physics to calculate the low energy effective Hamiltonian. It offers a
perturbative method to understand the renormalization effects in the strong
coupling regime of the quantum many-body models. The generator for
Schrieffer-Wolff transformation is calculated using heuristic methods. It is
highly desirable to have a rigorous, systematic and simple method for the
calculation of generator for this highly important transformation. In this
paper, we put forward such a method. We demonstrate our method by applying it
to few well-known models from various fields like strongly correlated electron
systems, quantum optics and cavity quantum electrodynamics. Our method can be
applied to a broad class of quantum many-body Hamiltonians.
