  Two complementary techniques are developed for obtaining the asymptotic form
of gravitational-wave data at large radii from numerical simulations, in the
form of easily implemented algorithms. It is shown that, without extrapolation,
near-field effects produce errors in extracted waveforms that can significantly
affect LIGO data analysis. The extrapolation techniques are discussed in the
context of Newman--Penrose data applied to extrapolation of waveforms from an
equal-mass, nonspinning black-hole binary simulation. The results of the two
methods are shown to agree within error estimates. The various benefits and
deficiencies of the methods are discussed.
