Abstract The purpose of the lectures that appear within this chapter is to provide the reader with an idea of how we can probe new physics with quark flavour observables using effective theory techniques. It begins by providing a concise review of the quark flavour structure of the standard model. Then it introduces the effective Hamiltonian for quark weak decays. Following on, it then considers the effective Hamiltonian for ?F=2 transitions in the standard model and beyond. It discusses how meson–anti–meson mixing and CP violation can be described in terms of the ?F=1 and ?F=2 effective Hamiltonians. Finally, it presents the Unitarity Triangle Analysis and discusses how very stringent constraints on new physics can be obtained from ?F=2 processes.