  Several alternative formulations of the first order approach to unimodular
gravity are presented. There is always a particular one such that it is {\em
classically} equivalent to the second order formulation; this we call {\em
educated}. It is often at variance with the {\em naive} approach, in which the
lagrangian is taken as given exactly by the same expression as in the second
order formulation; only the number and character of the independent variables
changes. Namely, typically some of the momenta are now considered as
coordinates. The ensuing Hamiltonians are thereby discussed and their physical
differences pointed out.

General Relativity and Quantum Cosmology