All you need is:
a long exposure camera
tripod
torch / flashlight
a dark night and a friend.
Hit the capture button on the camera and run behind your friend. (you may want to use the timer function here to give you plenty of time to prepare)
Once you're in position behind your friend, place the torch by their right foot and turn it on. Now you simply run the torch round their body making sure you keep a nice even speed and don't obstruct the torch with any loose clothing.
If you find you've completed you're outline before you hear the camera shutter, you can always add a little trail or you can simply turn off the torch when you have finished.