Making a subject glow

If they need to have a halo, you'd need a strong backlight. In addition, you could add some lighting in PS later, which you direct on their faces and calculate in 'soft light' mode. Don't forget to soften their skin a bit, too, to give them that candlelight look. You might also use a (turned down low) snoot light on their faces, to prevent overexposing but give them a gentle glow, maybe together with a gelled bulb.... be imaginative!

A gold reflector might be a nice touch to make the subject's skin glow, no matter their skin color. If you bounce your studio light off that reflector, you might like the look. I'd try putting the reflector overhead, or overhead at an angle, and bouncing light from below. You could test this at home with a light bulb and a sheet of aluminum foil over cardboard and see if you like the look. The foil won't give you the skin glow of the gold tone, but it will show you how the light reflection would work.

I assume you'll be using some sort of flourescent lighting for the "ugly" shots? Nobody looks good in that light!

A skin moisturizer tends to bring out the highlights in skin, and diffuse on-axis lighting (an umbrella directly above the camera) will spread those highlights. A less diffuse on-axis light will produce more brightness in the skin broadside-on to the camera and less in skin angled away from it (a soft box with a grid).
If the subject is posed against a dark background, a soft-focus lens such as a Portragon will spread the highlights over the background for a halo effect. You can get a similar effect with a blur layer in PS.
Don't use people--hire angels. ;-)

Wow thanks guys, that's really helpful!
I'll try using an on-axis softbox or diffuse flash above the camera with that moisturiser, Charles... we did study that lighting design in class, I think our teacher called it a "Hollywood" setup... and I love the idea of hiring angels and using a soft-focus lens, but sadly I don't think I can find either in time... :)
Since I can't find angels, I'm going to couple that with Monika's idea of using the strong backlight for the "halo" - I might try to spray a fine mist of hairspray or something behind them before I take each shot? And I'll shoot with the aperture wide open so the mist kinda blurs into a halo behind them? I might just have to experiment with that. :)
I definitely have a gold reflector in the studio, so I'll use that to fine-tune this setup and soften out any harsh shadows in the "beautiful" portrait.
I think I'll definitely do a fluorescent-lit shot for one of the ugly portraits, Jennifer. You're right, nobody looks very good in fluoro lighting! I'll use it to light the subject with harsh shadows and hopefully it will turn out properly ghastly. :)

For the soft-focus, in a pinch, I have used a little saliva on a skylight filter over my lens to remove a subject's wrinkles (please don't tell my mom). I understand that hand lotion or vaseline on the filter, or cellophane wrapped over the lens, are also decent substitutes and much more hygienic.

Hairspray is flammable, most kinds of dust create allergy eyes and worse, very fine water droplets work (the fog machine), and a bit of dry ice in alcohol creates too much fog and is cold enough to be dangerous--plus the CO2 can creep up on you. Jennifer's suggestions will work, and so will the time-honored expedient of breathing on your lens.
Amusing that your teacher calls the on-axis umbrella a Hollywood setup--I did casting shots in Hollywood for a number of years.

Well I had my first studio session yesterday! And I tried to put all your advice into practice.
Unfortunately, the set I had to work with was quite small - a kitchen setting - and I couldn't figure out a way to set up a backlight/hair light behind my models (some of my classmates) ... so I concentrated on the on-axis softbox and used a gold reflector to add a bit of extra warmth from the left. Some of the pictures turned out pretty well I think (for a first try!) but I'd appreciate any other advice anyone would like to provide, as I've been given two additional studio sessions next term (in three weeks time) to finish this assignment! :)

Leonard,

I think your lighting is very nice on these subjects.

FYI: Direct lighting (just above the nose - or "on the axis") has often been referred to "Hollywood" or "Butterfly" lighting as it was quite popular with "stars" in the 40's and creates a "butterfly" shaped shadow just under the nose. It is really quite a flattering lighting setup, especially when used with soft focus on females.

Mark