The PhotoArgus has this to say on controlling depth of field. One of the best known methods is, of course, lens aperture and I love (love, love, love!) how much room to play with depth of field my new lens (f/1.4) gives me.
These pictures are all straight from the camera and unedited, and serve no purpose other than me going ooooooh, depth of field. Yes, I’m about five sometimes.