  We briefly explain the consistency conditions imposed on the effective
holographic theories, which are parameterized by two real exponents
$(\gamma,\delta)$ that control the IR dynamics. The general scaling of DC
resistivity with temperature at low temperature and AC conductivity at low
frequency across the whole $(\gamma,\delta)$ plane are explained. There is a
codimension-one region where the DC resistivity is linear in the temperature.
For massive carriers, it is shown that when the scalar operator is not the
dilaton, the DC resistivity scales as the heat capacity (and entropy) for
$(2+1)$-dimensional systems. Regions are identified where the theory at finite
density is a Mott-like insulator. This contribution is based on arXiv:1005.4690
with emphasis on the transport properties of charged dilatonic black holes with
potential.
