Carrier sense multiple access (CSMA) protocols, such as the IEEE 802.11 protocol, are widely used in wireless ad hoc networks. In this paper, we consider how the parameters of such protocols should be selected. Our primary goal is an increase in spatial reuse. By analyzing conditions for collision prevention, we argue that the product of the transmit power and the carrier sense threshold should remain constant. We then discuss the practical implementation of this principle within the framework of the IEEE 802.11 protocol. Finally, we provide simulation results that compare our scheme to other methods of selecting the protocol parameters. These results indicate that an increase in spatial reuse can indeed be achieved.