  We present a universal physical picture for describing storage and retrieval
of photon wave packets in a Lambda-type atomic medium. This physical picture
encompasses a variety of different approaches to pulse storage ranging from
adiabatic reduction of the photon group velocity and pulse-propagation control
via off-resonant Raman fields to photon-echo based techniques. Furthermore, we
derive an optimal control strategy for storage and retrieval of a photon wave
packet of any given shape. All these approaches, when optimized, yield
identical maximum efficiencies, which only depend on the optical depth of the
medium.
