  Observations over the past decade have verified, beyond reasonable doubt,
that most galactic nuclei contain massive black holes. Hole masses are being
measured and firm evidence for spin is being sought. Attention is now returning
to the study of how gas flows around black holes and how energy is released
both from the accreting gas and from the hole itself in the form of radiation,
relativistic jets and non-relativistic, hydromagnetic winds. Some of the
different possibilities currently under investigation are briefly reviewed and
some recent clues from radio scintillation, polarization and X-ray observations
are discussed. It is argued that observations of persistent circular
polarisation in Sgr A$^\ast$ support the presence of an ordered disk magnetic
field. It is also conjectured that adiabatic, sub- and super-critical accretion
flows are demand-limited, not supply-driven and are associated with large mass
outflow as appears to be the case in Sgr A$^\ast$. This principle may have to
be modified when a massive black hole forms in a protogalaxy and this
modification may account for the proposed hole mass-bulge velocity dispersion
relation. The final stages of this process may release sufficient wind energy
from the nucleus to prevent disk formation.
