Ok, so my teacher did not explain this so well. Basically, from what I see, is this: A ligand induces the outermost d orbital to split into the t2g and eg orbitals. The energy difference between them is noted as Delta0. Delta0 varies based on the ligand, and is not findable a priori, without computers. You look Delta0 up in the spectrochemical series. If Delta0 is greater than the energy difference between the singlet and triplet states, then the electrons pair up in the t2g level. If it is less, then the spins are aligned, and the electrons do not pair up until the eg level is also half full. Have I missed anything? Also, what is the difference between ligand field theory and crystal field theory in terms of ligand-transition metal interactions? Thanks!