  Long distance effects are studied in the rare exclusive semileptonic
$B_{(d,s)}\to V \ell^+ \ell^-$ decays, where $V$ denotes a $K^*$ or $\phi$
meson. The form factors, which describe the meson transition amplitudes in the
effective Hamiltonian approach, are calculated by means of Ward identities,
experimental constraints and extrapolated within a general vector meson
dominance framework. These form factors are then compared to the ones obtained
in Lattice QCD simulations, with Light Cone Sum Rules and a Dyson-Schwinger
equation approach. Additionally, the $B_d\to K^* \ell^+ \ell^-$ and $B_s\to
\phi \ell^+ \ell^- $ branching ratios are computed and the differential
branching fractions are given as a function of the squared-momentum transfer.
