The vast majority of guitars produced today are built according to general principles laid down in the nineteenth century. Nevertheless, the devil is in the detail, and innovative makers constantly reappraise the design and construction of instruments in their endeavors to control quality or to seek ‘‘improvement.’’ The maker’s approach, necessarily, tends to be pragmatic, but it is one which can be greatly informed by the application of relatively simple acoustical models. This paper will examine various important design aspects—for example choice of materials, body size, strutting, soundboard thickness—introducing the basis for making informed decisions.