  We present a method that allows us to find asymptotic form of various
characteristics of disordered systems in the strong localization regime, i.e.,
when either the random potential is big enough or the energy is close enough to
the spectrum edges. The method is based on the hypothesis that relevant
realizations of the random potential in the strong localization regime have the
form of deep random wells that are uniformly and chaotically distributed in the
space with a sufficiently small density. Assuming this and using the density
expansion, we show first that the density of wells coincides in the leading
order with the density of states. Thus the density of states is in fact the
small parameter of the theory in the strong localization regime. Then we derive
the Mott formula for the low frequency conductivity and the asymptotic formulas
for certain two-point correlators when the difference of respective energies is
small.
