Essentially you should look for a solid, light backdrop. White seamless paper or a white wall will do the trick, or, as you can see in this image just below, snow works very well. This image of Burton was shot in the snows of last winter. The shot is overexposed, on purpose, to blow out the shadows and eliminate some of the contrast. Since Burton is mostly white, the outlines of his body blended into the very bright snow as well once I overexposed the shot.
Sassy, a visiting setter who came to stay with us on Sunday for the day, was my subject. She is eight years old and a lovely girl. The day was a bit overcast, but there were breaks in the clouds when sunshine came through. The background is our patio, which I have completely washed out in post processing. I used an open shutter on a 50mm 1.8 lens. I then used my levels and contrast adjustments to tweak the image into high key. There are a few shadows below her chin and to the left, but the image is still dramatic and qualifies as high key.
to catch her high key images!