  We characterize the evolution of spectral and temporal properties of several
Galactic black hole transients during outburst decay using the data from well
sampled PCA/\rxte observations close to the transition to the low/hard state.
We find several global patterns of evolution for spectral and temporal
parameters before, during, and after the transition. We show that the changes
in temporal properties (sudden increase or decrease in the rms amplitude of
variability) are much sharper than the changes in the spectral properties, and
it is much easier to identify a state transition with the temporal properties.
  The spectral index shows a drop 3-5 days before the transition for some of
our sources. The ratio of the power-law flux to the total flux in the 3-25 keV
band increases close to the transition, which may mean that the system must be
dominated by the coronal emission for the transition to occur. We also show
that the power-law flux shows a sharp change along with the temporal properties
during the transitions which may indicate a threshold transition volume for the
corona. The evolution of the spectral and temporal properties after the
transition is consistent with the idea that the inner accretion disk moves away
from the black hole. Based on the evolution of spectral and temporal parameters
and changes during the transitions, we discuss possible scenarios of how the
transition is happening.
