I happen to really like doing portraits made using only available daylight (as opposed to artificial lights: strobes, hot lights, etc.). It made sense then that I watched (on lynda.com) the video "Douglas Kirkland on Photography: Natural Light Portraiture" hoping to gain some tips from a renowned photographer. I came in with the expectation of learning tip after tip, like in an instructional video, but instead I found myself watching a master just doing his thing.
The video takes place in four locations within and around Kirkland's house. The first location is accidental as Kirkland realizes that the dressing room his subject is sitting in is casting beautiful light on the her. The second scene takes place in the living room that has directional light coming in from a skylight. Outdoors, he uses a diffuser/white tent and a canopied daybed. Despite having assistants to help him with make up, reflectors, and backgrounds, the tips he gives can apply to anyone interested in doing natural light portraits.
Practical tips he mentions include forming a tripod with one's arm and leg when in a seated position, using a longer lens to prevent distortion and to soften the background, and taking pictures without the intention of fixing it in post production (or doing minimal work in Photoshop).
He emphasizes that the relationship with the subject is important as exhibited by his constant attention to his subject comfort and his encouraging words. For example, he peppers her with compliments to keep her feeling relaxed and good about herself. When in the uncomfortable situation of having light in her eyes, he has her close them, only to open them back up after a countdown, so that he still gets the shot.
He concludes that we have to learn to recognize good natural light and not to attempt to alter it (e.g., add extra fill lights). If we do, changes must be "delicate" since "less is more."