  An introduction to spin techniques in particle physics is given. Among the
topics covered are: helicity formalism and its applications to the decay and
scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity
amplitudes (including projection operator methods and the spinor helicity
method), and density matrix techniques. The utility of polarization and spin
correlations for untangling new physics beyond the Standard Model at future
colliders such as the LHC and a high energy $e^+e^-$ linear collider is then
considered. A number of detailed examples are explored including the search for
low-energy supersymmetry, a non-minimal Higgs boson sector, and new gauge
bosons beyond the $W^\pm$ and $Z$.
