  Chiral perturbation theory (CPT), the low-energy effective theory of QCD, can
be used to describe QCD observables in the low-energy region in a
model-independent way. At any given order in the chiral expansion, CPT
introduces a finite number of parameters that encode the short-distance physics
and that must be determined from experiment or numerical lattice QCD
simulations. In this thesis, we calculate a number of hadronic observables in
the quenched and partially quenched versions of CPT:
  Chiral corrections to B^(*) --> D^(*) at zero recoil are investigated in
quenched CPT. We study in detail the charge radii of the meson and baryon
octets, electromagnetic properties of the baryon decuplet, and the baryon
decuplet to octet electromagnetic transitions in both, quenched and partially
quenched CPT. We further show how effects due to the finite size of the lattice
can be accounted for in heavy meson CPT and calculate, as explicit examples,
neutral B meson mixing and the heavy-light meson decay constants. We also
demonstrate how one can account for effects due to finite lattice spacing in
the low-energy theories, considering as an example electromagnetic meson and
baryon properties.
  The results of our calculations are crucial to extrapolate quenched and
partially quenched lattice data from the heavier light quark masses used on the
lattice to the physical values.
