A net in the group algebra of a locally compact group which
commutes asymptotically with elements from the measure algebra is
called quasi-central. In this paper we provide new
characterizations of locally compact groups whose group algebras
possess quasi-central bounded approximate identities.
Reiter-type and structural conditions for such
groups are obtained which indicate that these groups behave much
like the tractable [SIN]-groups. A general notion of an amenable
action on the predual of a von Neumann algebra is developed to
prove these theorems. Applications to the cohomology of group and
Fourier algebras are discussed.