  The evolutionary sequence for high-mass star formation starts with massive
starless clumps that go on to form protostellar, young stellar objects and then
compact HII regions. While there are many examples of the three later stages,
the very early stages have proved to be elusive. We follow-up a sample of 110
mid-infrared dark clumps selected from the ATLASGAL catalogue with the IRAM
telescope in an effort to identify a robust sample of massive starless clumps.
We have used the HCO+ (1-0) and HNC (1-0) transitions to identify clumps
associated with infall motion and the SiO (2-1) transition to identity outflow
candidates. We have found blue asymmetric line profile in 65% of the sample,
and have measured the infall velocities and mass infall rates (0.6-$36 \times
10^{-3}$ Msun/yr) for 33 of these clumps. We find a trend for the mass infall
rate decreasing with an increase of bolometric luminosity to clump mass i.e.
star formation within the clumps evolves. Using the SiO 2-1 line, we have
identified good outflow candidates. Combining the infall and outflow tracers
reveals that 67% of quiescent clumps are already undergoing gravitational
collapse or are associated with star formation; these clumps provide us with
our best opportunity to determined the initial conditions and study the
earliest stages of massive star formation. Finally, we provide an overview of a
systematic high-resolution ALMA study of quiescent clumps selected that allows
us to develop a detailed understanding of earliest stages and their subsequent
evolution.
