So you can see it is selecting my shirt there and it is not quite getting all of it.
With the instant alpha tool you can grab a color and you can select it. The first way probably won't work really well for this image is to use this instant alpha tool. I'm going to go to the Tools here and turn that on. Using Preview version 7 I'm going to show you how to cut out part of an image, like somebody from an image, and perhaps paste it somewhere else. Let me show you how you can cut out objects from images in Preview. Check out Cutting Out Part Of an Image With Preview at YouTube for closed captioning and more options.