In the emerging field of synthetic biology, a central goal is to reliably engineer bacteria to respond to environmental signals according to a pre-determined genetic program. The sensor systems and genetic circuitry inside bacteria are the 'eyes' and 'brain' of a new class of biotechnological applications in which bacteria are used as living, self-replicating computers that can beneficially interact with the physical world. These engineered gene networks are constructed by extracting natural sensor systems and other genetic parts from multiple organisms and recombining them into novel configurations. This chapter is a how-to guide. It describes several strategies for engineering new bacterial sensor systems and synthetic gene networks that are capable of sensing a desired stimulus and generating interesting dynamical or pattern-forming responses. We also provide specification sheets describing many two-component and quorum-sensing systems, focusing on the information that one needs to know in order to use them for engineering applications.