Aspects of moduli stabilisation in string and M-theory

In this thesis we study compactifications of type II string theories and M-theory to four dimensions. We construct the four-dimensional N=2 supergravities that arise from compactifications of type IIA string theory and M-theory on manifolds with SU(3)-structure. We then study their potential for moduli stabilisation and give explicit examples where all the moduli are stabilised. We also study the effective action for type IIB conifold transitions on Calabi-Yau manifolds. We find that, although there are small regions in phase space that lead to a completed transition, generically the moduli are classically trapped at the conifold point thereby halting the transition.