The hyperfocal distance is the focus setting that will give you the greatest depth of field (DOF) that still includes infinity. If your lens has a DOF scale (a series of inscribed lines adjacent to the distance scale and labeled with f-numbers), setting it is easy: Switch the lens to manual focus and turn it so that the infinity distance mark lines up with the f-stop you're using. If your lens has no DOF scale, you can eyeball it using DOF preview (provided your camera has it): Set your aperture and trigger DOF preview. Focus the lens manually to a near distance, and, while looking through the viewfinder, set the distance farther and farther until the most distant object comes just into focus. If the viewfinder image is too dark, cover the finder, cup your hands around the eyepiece, and wait for your eye to adjust.
(From 5 Nature Shooting Skills April 2009 issue)_