You’ll need two cameras for this trick: one (preferably digital) to take the picture and another to aim through. Most people seem to favor cameras with waist-level viewfinders because they’re large and easy to see.
Frame your shot using the older camera, then aim your digital camera at the viewfinder and take the picture. Afterwards, crop the photo to take out everything but the viewfinder image.
I made a little "smokestack" out of file folders and painters tape in order to block out the light and reduce the glare on the lens.