  The presence of localized spins exerts a strong influence on quantum
localization in doped semiconductors. At the same time carrier-mediated
interactions between the localized spins are modified or even halted by
carriers' localization. The interplay of these effects is discussed for II-VI
and III-V diluted magnetic semiconductors. This insight is exploited to
interpret the complex dependence of resistance on temperature, magnetic field,
and concentration of valence-band holes in (Ga,Mn)As. In particular, high field
negative magnetoresistance results from the orbital weak localization effect.
The resistance maximum and the associated negative magnetoresistance near the
Curie temperature are assigned to the destructive influence of preformed
ferromagnetic bubbles on the "antilocalization" effect driven by
disorder-modified carrier-carrier interactions. These interactions account also
for the low-temperature increase of resistance. Furthermore, the sensitivity of
conductance to spin splitting and to scattering by spin disorder may explain
resistance anomalies at coercive fields, where relative directions of external
and molecular fields change.
