  We study the application of the classical equations of motion (EOM) within
the framework of an effective low-energy Lagrangian treated at the loop level.
Gauge-fixing and ghost terms, which enter naturally in the EOM, are found to
lead to no physical effects --- neither through operator mixing nor in matrix
elements. Beyond first order in the effective interactions, contact terms have
to be included when reducing the effective Lagrangian and we present an
explicit procedure to construct them. Applied to (hadronic) rare B-decays, the
EOM drastically simplify the effective Lagrangian and its matching to the
underlying theory, and certain cancellations of large (logarithmic)
contributions become more transparent. Finally, we discuss details of the
`matching' of the effective Lagrangian, which may be helpful in incorporating
short distance QCD corrections in further phenomenological studies.
