The surface tension of liquid crystals at the free surface has been found experimentally to exhibit intriguing behavior in the neighborhood of the nematic-isotropic transition temperature TNI. We discuss general features of the relation between wetting properties and temperature dependence of the free surface tension close to TNI. Different wetting properties are expected to yield a varied assortment of surface tension characteristics. In order to supplement and extend these arguments, we have analyzed the surface tension using a microscopic density functional model. In this approach anisotropic volume exclusion effects are neglected, isolating instead the effect on the surface tension of the orientationally coupled Lennard-Jones potential. Wetting properties are sensitive to the different spherical harmonic components of this potential, and thus the model exhibits a rich array of surface tension behaviors, of which we give a brief overview. The principal new result of the calculations we have performed, summarized here, is the appearance of a pre-transitional surface tension minimum which is seen in many experimental studies. This is related to anomalously high sub- surface order.