You have been given alot of good tips here, but I thought it might be worth mentioning that it can also be done in the editing stage on the computer.
Take your photo using an aperture that will have the whole lot (or most of it) in focus. Then load up the photo in Photoshop (or similar programme) and select all the fore ground to be blurredand apply the filter. I don't have Photoshop on this computer so I can't check, but I think there is an option to have the blur lessen in effect as it moves away from a centre point. Useful if you want the image to slowly come into focus as you move back.
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