This chapter discusses how to take advantage of optimal control theory to minimize the entropy production of process units, in a step-wise, practical approach. The main results from literature are discussed, e.g. the validity of the theorems of equipartition of entropy production or equipartition of forces, as approximations to the state of minimum entropy production. A common property of systems with possibilities for internal equilibration seems to be that operating paths with minimum entropy production constitute bands in state space, called highways in state space. We show how energy-efficient design can be facilitated with knowledge of these properties.