  In this work, we establish a new method to find critical points of
differentiable functionals defined in Banach spaces which belong to a suitable
class ($\mathcal{J}$) of functionals. Once given a functional $J$ in the class
($\mathcal{J}$), the central idea of the referred method consists in defining a
real function $\zeta$ of a real variable, called {\it energy function}, which
is naturally associated to $J$ in the sense that the existence of real critical
points for $\zeta$ guarantees the existence of critical points for the
functional $J$. As a consequence, we are able to solve some variational
elliptic problems, whose associated energy functional belongs to
($\mathcal{J}$) and provide a version of the mountain pass theorem for
functionals in the class ($\mathcal{J}$) that allows us to obtain mountain pass
solutions without the so-called Ambrosetti-Rabinowitz condition.
