  The effective theory based on combined chiral and heavy quark symmetry, the
heavy meson chiral perturbation theory, is applied to studying the role of
resonances in various processes of heavy mesons within and beyond the Standard
Model. Chiral corrections including both positive and negative parity heavy
meson doublets are calculated to the effective strong couplings featuring in
the effective theory leading order interaction Lagrangian, to the Isgur-Wise
functions in semileptonic B to D decays and to the complete set of
supersymmetric four-quark operators mediating heavy neutral meson mixing. Bare
values of the effective strong couplings are extracted from the measured decay
widths of charmed resonances. Chiral behavior of the couplings, Isgur-Wise
functions and heavy meson bag parameters is studied in the leading logarithmic
approximation. In semileptonic heavy to light decays we determine resonance
contributions to the various form factors within an effective theory inspired
model at zero recoil. We employ a form factor parameterization based on
effective theory limits to extrapolate our results to the whole kinematical
region in charm decays. We compare our results with experimental data and
lattice calculations. Very rare nonleptonic decays of the B_c meson are studied
within the Standard Model where they are mediated by box loop diagrams, and
within a number of Standard Model extensions. Based on existing experimental
searches for related B meson decays, limits are imposed on some of the models
studied. The most promissing nonleptonic two- and three-body decay channels of
the B_c meson in the search for such new physics contributions are identified.
