Most point and shoot cameras have a minimum focal distance of about 2.5-3 feet, so any closer than that, it will be out of focus.

Some cameras have a macro setting (usually represented by a little flower). This will allow a minimal focal length of a couple inches or sometimes closer. Like Icygirl said, play around with the settings. If you still have the manual, read it.

If your camera has a zoom lens, have a friend take the pic by standing more than 3 feet away, but zooming in.
Don't bother with digital zoom on a digital camera. All that does is crop the image, which you can do post-processing if you really need to. Either way, the image will lose resolution and quality.