  Fundamental differences in the prediction of reaction rates with intermediate
and heavy target nuclei compared to the ones with light nuclei are discussed,
with special emphasis on stellar modifications of the rates. Ground and excited
state contributions to the stellar rates are quantified, deriving a linear
weighting of excited state contributions despite of a Boltzmann population of
the nuclear states. A Coulomb suppression effect of the excited state
contributions is identified, acting against the usual Q-value rule in some
reactions. The proper inclusion of experimental data in revised stellar rates
is shown, containing revised uncertainties. An application to the s-process
shows that the actual uncertainties in the neutron capture rates are larger
than would be expected from the experimental errors alone. Sensitivities of
reaction rates and cross sections are defined and their application in reaction
studies is discussed. The conclusion provides a guide to experiment as well as
theory on how to best improve the rates used in astrophysical simulations and
how to assess their uncertainties.
