Leading lines give your images dramatic motion and energy. I use my lines to take the viewer by the hand lead them into the image and point out a critical feature or subject. This captures their attention and forcing them to pay attention to what is being seen.
I generally prefer to use diagonal lines when possible because diagonals demand attention, this is why the warning signs on the road are triangles and diamonds. Even if they are only seen in peripheral vision diagonal lines irresistibly attract the eye.
Photos seen here are: top left Granite Bay Bank for Williams + Paddon Architects + Planners, top right Millenium Building for Williams + Paddon Architects + Planners, lower left Mather Hospital for Nacht & Lewiss Architects, and Private Residence for Viscusi Elson Interior Design.