Semiconductor microcavities offer the possibility to enhance the interaction between cavity photons and elementary excitations of the semiconductor. The excitations considered here are excitons, bound states of electrons and holes. The coherent interaction between these excitons and photons leads to the formation of quasiparticles called exciton-polaritons. The respective interaction regime is termed strong coupling regime. Exciton-polaritons inherit properties from both their photonic and their electronic component. A typical property inherited from the excitons is the spin. The scope of this thesis is twofold. On the one hand, the general properties of exciton-polaritons are studied theoretically. On the other hand, the influence of the exciton spin is analyzed. Several effects and tools known from nonlinear dynamics such as pattern formation, cavity solitons, domain walls, perturbation theory, and bifurcation theory are used in order to highlight these properties. The findings of this thesis expand the knowledge about the theoretical foundations of polariton physics. This may pave the way to potential application of semiconductor microcavities as all-optical information processing and storage devices.