  The Hubble constant, H0, or its dimensionless equivalent, "little h", is a
fundamental cosmological property that is now known to an accuracy better than
a few percent. Despite its cosmological nature, little h commonly appears in
the measured properties of individual galaxies. This can pose unique challenges
for users of such data, particularly with survey data. In this paper we show
how little h arises in the measurement of galaxies, how to compare
like-properties from different datasets that have assumed different little h
cosmologies, and how to fairly compare theoretical data with observed data,
where little h can manifest in vastly different ways. This last point is
particularly important when observations are used to calibrate galaxy formation
models, as calibrating with the wrong (or no) little h can lead to disastrous
results when the model is later converted to the correct h cosmology. We argue
that in this modern age little h is an anachronism, being one of least
uncertain parameters in astrophysics, and we propose that observers and
theorists instead treat this uncertainty like any other. We conclude with a
"cheat sheet" of nine points that should be followed when dealing with little h
in data analysis.
