  Although low-dimensional $S = 1$ antiferromagnets remain of great interest,
difficulty in obtaining high-quality single crystals of the newest materials
hinders experimental research in this area. Polycrystalline samples are more
readily produced, but there are inherent problems in extracting the magnetic
properties of anisotropic systems from powder data. Following a discussion of
the effect of powder-averaging on various measurement techniques, we present a
methodology to overcome this issue using thermodynamic measurements. In
particular we focus on whether it is possible to characterise the magnetic
properties of polycrystalline, anisotropic samples using readily available
laboratory equipment. We test the efficacy of our method using the magnets
[Ni(H$_{2}$O)$_{2}$(3,5-lutidine)$_{4}$](BF$_{4}$)$_{2}$ and
Ni(H$_{2}$O)$_{2}$(acetate)$_{2}$(4-picoline)$_{2}$, which have negligible
exchange interactions, as well as the antiferromagnet
[Ni(H$_{2}$O)$_{2}$(pyrazine)$_{2}$](BF$_{4}$)$_{2}$, and show that we are able
to extract the anisotropy parameters in each case. The results obtained from
the thermodynamic measurements are checked against electron-spin resonance and
neutron diffraction. We also present a density functional method, which
incorporates spin-orbit coupling to estimate the size of the anisotropy in
[Ni(H$_{2}$O)$_{2}$(pyrazine)$_{2}$](BF$_{4}$)$_{2}$.
