Using the off camera flash as a hair light

How does one position it?  Ideally high on a light stand and pointed at the top of the subject's head. 

How strong is the flash?  Not too strong as the angle will make it brighter than it actually is.  Also, hair color has an effect.  It's brighter on blonds vs. brunettes.

How high?  With my stands, I can go to about 8' or 9' above the subject. 

What happens if it's too low?  The flash will go into your lens and cause flare.

 This is what happens when the hair light is too low.  You get lens flare.  Some people like flare.  I don't.

Here's a setup of a recent portrait shoot.  It was sunny outdoors but the wind was howling.  I had to do about 20+ portraits of a group of pageant contestants.  The only place that looked decent was this corner with the rock wall.  The hair light was put on a stand and raised to the highest point of the light stand.  Flash was a Canon 550EX at 1/128 power.

The light source for the portrait was the outdoors coming in through the windows.  Because there was a roof overhead, the light direction was at the proper angle from the front and back of the subject.

By using a long telephoto, it compressed the background so no extraneous items appeared on the side.  Care had to be taken so the angle was correct.  Subject was also placed away from the background so the rock wall would kind of go out of focus.  Exposure was 1/200, f2.8 ISO 200

The final result.  You can also see that the flash for the hair light also illuminated the rock wall and there was a kicker light coming in from the window behind the subject.

What's a kicker light?  Come back later and see in a future post.