  Recent ground based deep observations of the Universe have discovered
populations of massive quiescent galaxies at $z\sim3-5$. The observed number
density of sources are higher than predicted by cosmological models. Thus,
constraining the formation and evolutionary mechanisms of these galaxies is
crucial to determine how the Universe built such massive galaxies early in the
Universe and what mechanisms drove the cessation of star-formation. With the
scheduled launch of the James Webb Space Telescope, observations of rest-frame
optical features of $z\sim3-5$ galaxies will be enabled through the continuous
$0.6 - 5.3\mu m$ coverage of the on-board NIRSpec instrument. Here we perform
mock JWST/NIRSpec observations to determine optimal observing strategies to
efficiently recover the completeness, star-formation histories, element
abundances, and the initial mass function of massive quiescent galaxies in this
cosmic window. We show that through smart grism/filter choices, NIRSpec slit
and integral field spectroscopy observations can be used to constrain formation
pathways of these galaxies to high accuracy with high efficiency. Such
observations could revolutionize our understanding of galaxy evolution in the
early Universe providing much needed constraints to galaxy evolutionary models
in the early Universe.
