  Several reasonably model-independent formulations of the implications of new
physics for precision electroweak measurements have been developed over the
past years, most notably by Peskin and Takeuchi, and by Altarelli \etal. These
formulations work by identifying a small, but useful, set of parameters through
which new physics often enters into well-measured physical observables. For the
theories to which such an analysis applies, this approach greatly streamlines
the confrontation with the data. Since the experimentally-allowed range for
these parameters has been determined from global fits to the data, theorists
need only compute their predictions for these parameters to constrain their
models. These methods are summarized here, together with several recent
generalizations which permit applications to wider classes of new physics, and
which include the original approaches as special cases.
