  Using a QCD relativistic potential model, previously applied to the
calculation of the heavy meson leptonic constants, we evaluate the form factors
governing the exclusive decays $B\to\rho\ell\nu$, $B\to K^*\gamma$ and $B\to
K^*\ell^+\ell^-$. In our approach the heavy meson is described as a $Q\bar q$
bound state, whose wave function is solution of the relativistic Salpeter
equation, with an instantaneous potential displaying Coulombic behaviour at
small distances and linear behaviour at large distances. The light vector meson
is described by using a vector current interpolating field, according to the
Vector Meson Dominance assumption. A Pauli-Villars regularized propagator is
assumed for the quarks not constituting the heavy meson. Our procedure allows
to avoid the description of the light meson in terms of wave function and
constituent quarks, and consequently the problem of boosting the light meson
wave function.
  Assuming as an input the experimental results on $B\to K^*\gamma$, we
evaluate all the form factors describing the $B\to \rho, K^*$ semileptonic and
rare transitions. The overall comparison with the data, whenever available, is
satisfactory.
