  The Ising and BEG models critical behavior is analyzed in 2D and 3D by means
of a renormalization group scheme on small clusters made of a few lattice
cells. Different kinds of cells are proposed for both ordered and disordered
model cases. In particular, cells preserving a possible antiferromagnetic
ordering under decimation allow for the determination of the N\'eel critical
point and its scaling indices. These also provide more reliable estimates of
the Curie fixed point than those obtained using cells preserving only the
ferromagnetic ordering. In all studied dimensions, the present procedure does
not yield the strong disorder critical point corresponding to the transition to
the spin-glass phase. This limitation is thoroughly analyzed and motivated.
