The image quality, performance and long-term stability of an optical system depends on a number of factors including the optomechanical design, and fabrication and thermal stabilization methods used for making the optical components and support structures. The distortion of optics due to mounting and the differential thermal expansion as a result of temperature changes is by far the biggest sources of image degradation. In all-reflective and catadioptric systems consisting of spherical and aspherical mirrors, very small stress induced at the mounting interface can adversely degrade the surface figure of a mirror, thereby causing significant image distortion and a severe drop in the system MTF. This paper presents a number of design techniques for mirror mount, which have been successfully used to greatly reduce or isolate the mounting stresses and, thereby, resulting in a minimal degradation of mirror surface figure. Some of these methods include using flexures, dowel pins, precision machining of the interfaces, and providing cut-outs to isolate the stresses from clamping screws used for securing the mirrors to support structures. Various mounting design options are presented especially for diamond-machined metal mirrors.