  We investigate the decay properties of some beauty and charm mesons with a
phenomenological potential model. First, we consider the nonrelativistic
Hamiltonian of the mesonic system with Coulomb plus exponential terms and study
the wave function and the energy of the system using the variational approach.
Thereby, we compute the masses, the decay constants, the leptonic branching
fractions of heavy-light mesons and the mixing mass parameter $\Delta
{m_{{B_q}}}$. We study the radiative leptonic decay widths of ${D_s} \to \gamma
\ell \bar \nu $, ${D^ - } \to \gamma \ell \bar \nu $ and the semileptonic decay
widths of ${\bar B_{(s)}} \to {D_{(s)}}\ell \bar \nu $, ${\bar B_{(s)}} \to
D_{(s)}^*\ell \bar \nu $. Using Isgur-Wise functions, we calculate the
branching ratios of $B \to {D^{(*)}}\pi $ and two-body nonleptonic decay of $D
\to K\pi $. Our results are consistent with other theoretical models and the
experimental results.
