  We show how to systematically apply the Faddeev-Jackiw symplectic method to
General Relativity (GR) and to GR extensions. This provides a new coherent
frame for Hamiltonian analyses of gravitational theories. The emphasis is on
the classical dynamics, uncovering the constraints, the gauge transformations
and the number of degrees of freedom; but the method results are also relevant
for canonical quantization approaches. We illustrate the method with three
applications: GR and to two Brans-Dicke cases (the standard case $\omega \not=
- 3/2$ and the case with one less degree of freedom, $\omega = - 3/2$). We
clarify subtleties of the symplectic approach and comment on previous
symplectic-based Hamiltonian analyses of extended theories of gravity, pointing
out that the present approach is systematic, complete and robust.
