  We study the operator product expansion (OPE) and quark-hadron duality for 2-
and 3-point correlators of the axial (A) and pseudoscalar (P) currents of the
light quarks. In the chiral limit these correlators are often dominated by
nonperturbative power corrections leading to subtleties of quark-hadron duality
relations and of the extraction of properties of light pseudoscalars. For the
2-point correlators, we show the sum rule for $<PP>$ to be sensitive to the
excited light pseudoscalar. For the 3-point correlators, we derive the Ward
identites which provide the normalization of the pion electromagnetic form
factor at zero momentum transfer. For large momentum transfer, we demonstrate
the way the correct behaviour of the pion form factor in agreement with
perturbative QCD emerges from condensate terms in the OPE for the $<PVP>$ and
$<AVP>$ correlators. The local-duality sum rule for $<AVA>$ is shown to lead to
the pion form factor with the required properties for all values of the
momentum transfer.
