  Systematic surveys are being proposed to discover a significant number of
galaxies at z ~ 6, which is now suggested as the epoch when the reionization
era of the Universe ends. To plan such surveys, we need a reasonable
expectation of the surface density of high redshift galaxies at different flux
limits. Here we present a simple prediction of the surface density of 5.5 < z <
6.5 galaxies in the optical regime, extrapolating from what is already known
about galaxies at z ~ 3. This prediction is consistent with the results of
nearly all known searches for objects at z ~ 6, giving confidence that we may
use it to plan optimal combination of survey depth and sky coverage in
searching for such objects. We suggest that the most efficient strategy with
existing ground-based facilities is to do medium-depth (m_{AB}= 24.0 -- 24.5
mag), wide-field (a couple of square degrees) survey using a wide-field camera
at a 4m-class telescope. As the predicted surface density at this brightness
level is very sensitive to the value of L*, the result of such a survey can be
easily used to constrain the luminosity evolution from z ~ 3 to 6.
