  Electronic transport in nanodevices is commonly studied theoretically and
numerically within the Landauer-B\"uttiker formalism: a device is characterized
by its scattering properties to and from reservoirs connected by perfect
semi-infinite leads, and transport quantities are derived from the scattering
matrix. In some respects, however, the device becomes a "black box" as one only
analyses what goes in and out. Here we use the Husimi function as a
complementary tool for quantitatively understanding transport in graphene
nanodevices. It is a phase space representation of the scattering wavefunctions
that allows to link the scattering matrix to a more semiclassical and intuitive
description and gain additional insight in to the transport process. In this
article we use the Husimi function to analyze some of the fascinating
electronic transport properties of graphene, \emph{Klein tunneling} and
\emph{intervalley scattering}, in two exemplary graphene nanodevices. By this
we demonstrate the usefulness of the Husimi function in electronic nanodevices
and present novel results e.g. on Klein tunneling outside the Dirac regime and
intervalley scattering at a pn-junction and a tilted graphene edge.
