  We discuss techniques to engineer effective long-range interactions between
polar molecules using external static electric and microwave fields. We
consider a setup where molecules are trapped in a two-dimensional pancake
geometry by a far-off-resonance optical trap, which ensures the stability of
the dipolar collisions. We detail how to modify the shape and the strength of
the long-range part of interaction potentials, which can be utilized to realize
interesting quantum phases in the context of cold molecular gases.
