Architects must translate domain requirements, external constraints, speculative popularity, and a host of other factors to determine the key _characteristics_ of a software system: performance, scale, elasticity, and so on. Yet architects must also analyze the _tradeoffs_ each characteristics entails, arriving at a design that manages to maximize as many beneficial properties as possible. This session describes how architects can identify architectural characteristics from a variety of sources, how to distinguish architectural characteristics from domain requirements, and how to build protection mechanisms around key characteristics. This session also describe a variety of tradeoff analysis techniques for architects, to try to best balance all the competing concerns on software projects.