  Gas-dynamical studies using the Hubble Space Telescope are an integral
component for future progress in the search for massive black holes in galactic
nuclei. Here we present an extensive set of gas rotation curves obtained with
the Space Telescope Imaging Spectrograph for the central regions of 23 disk
galaxies. We find that the bulges of randomly selected, nearby spiral and S0
galaxies generally do not contain well-defined gaseous disks. Only 15%-20% of
disk galaxies have regular, symmetric velocity fields useful for dynamical
analysis. Through comparison of the kinematics with Hubble Space Telescope
images of the nuclear regions, we show that the probability of success can be
significantly boosted by preselecting objects whose central dust lanes follow a
well-ordered, circularly symmetric pattern. The dust morphology can be
ascertained efficiently by visual inspection of unsharp-masked images.
