Halo is created by diffused light entering the aperture. This can be accomplished with large aperture and/or shallow depth of field, meanwhile using a diffused light source from behind.

If you want the glow have sharp details inside like the one on the picture, you will have to use large(r) aperture. If you want the glow kinds of soften the edges, you can play with aperture or DOF.

Use a softbox from behind, this creates an evenly lit, diffused light area. By itself, the softbox can create sufficient diffusion to have your glow effect. Now, try to make photos in RAW, watch out for not clipping at the top of your histogram. If you want to make the effect more noticeable, use larger aperture (and compensate with shutter, ISO - and if your shutter would go over your strobe sync rating, you will have to decrease the power of the softbox.)

Now, when you are happy with the effect, get another light source of your choice (simple flash, beauty dish, or even better, another soft box :-) ), and now change only that to have the face lit properly. Again, watch out for clipping at the top. If you cannot lit the face properly, decrease the softbox power from behind a bit, and start again, eventually you will have a nice, balanced photo.

You can use any diffuser instead of using a softbox, but the larger and even the lit area is, the better. You can use even a far source directed on a non-glossy white wall or backdrop or some white textile. You can even use very bright clouds as a matter of fact, but it is harder to tune the power of light of those... ;-) :-)

One additional note: if you shoot in RAW, you can create single-photo HDRs, and HDR can be used to create this glow/halo around points which are above the maximum white point of your result picture, and the glow or halo is stronger if the HDR intenstity is stronger...

(And a comment to your photo: you see the glow around the head because the hair acts like a diffuser - you can use hair, fur, etc. to diffuse light.)