  We reformulate the calculation of the dark matter-nucleon scattering cross
sections based on the method of effective field theories. We assume that the
scatterings are induced by the exchange of colored mediators, and construct the
effective theories by integrating out the colored particles. All of the leading
order matching conditions as well as the renormalization group equations are
presented. We consider a Majorana fermion, and real scalar and vector bosons
for the dark matter and show the results for each case. The treatment for the
twist-2 operators is discussed in detail, and it is shown that the scale of
evaluating their nucleon matrix elements does not have to be the hadronic
scale. The effects of the QCD corrections are evaluated on the assumption that
the masses of the colored mediators are much heavier than the electroweak
scale. Our formulation is systematic and model-independent, and thus suitable
to be implemented in numerical packages, such as micrOMEGAs and DarkSUSY.
