  An electrodynamic technique is developed for determining the components of
surface impedance and complex conductivity tensors of HTSC single crystals on
the basis of measured quantities of a quality factor and a resonator frequency
shift. A simple formula is obtained for a geometrical factor of a crystal in
the form of a plate with dimensions $b\gg a>c$ in a microwave magnetic field
${\bf H_{\omega}}\perp ab$. To obtain the c-axis complex conductivity from
measurements at ${\bf H_{\omega}}\parallel ab$ we propose a procedure which
takes account of sample size effects. With the aid of the technique involved
temperature dependences of all impedance and conductivity tensors components of
YBa$_2$Cu$_3$O$_{6.95}$ single crystal, grown in BaZrO$_3$ crucible, are
determined at a frequency of $f=9.4$ GHz in its normal and superconducting
states. All of them proved to be linear at $T<T_c/2$, and their extrapolation
to zero temperature gives the values of residual surface resistance
$R_{ab}(0)\approx 40$ $\mu\Omega$ and $R_c(0)\approx 0.8$ m$\Omega$ and
magnetic field penetration depth $\lambda_{ab}(0)\approx 150$ nm and
$\lambda_c(0)\approx 1.55$ $\mu$m.
