I've put together a short video to explain how to do it.
So, when you're taking pics like this it's very hit and miss. Open up your aperture to a low f number for great depth of field effects, but if you need a bit of elbow room, tighten up the aperture and frame your subject against a background that is far away, for easier results.
The trick is to take lots, and lots of photo's. Then take some more. Don't be discouraged if the first ones look rubbish, keep going, photographers luck will kick in and you'll get some great captures.