Don’t fight the light!
I often have to ‘travel light’ to shoots and that sometimes means leaving some of my favourite bits of kit behind. I’m always very twitchy about leaving lighting units out of my kit bag as having control of your light when shooting an interview means one less thing for you to worry about. Clients often suggest shooting an interview against a window (to enjoy the view) but unless you are packing serious light the result are normally pretty dire. The background is nearly always going to be brighter than your subject.
Make use of the natural light available in your location and position your subject into the light rather than away from it.
At an event in London recently there was lots of natural light streaming through the windows. I had to move quickly and there was no scope for putting up lights. So I decided to make use of the available light. When faced directly into the light it was a bit harsh but by positioning the subject at an angle to the window I quickly managed to achieve a well balanced shot.