When photographing a person on a white or plain background (or even on location if the background is simple), the choice of cropping can often help, but also sometimes hurt, the sales potential of an image.

A tight, dramatic crop like this one can be great, giving impact and tension to an image.

© Blend Images/Andersen Ross/drr.net

However it's still very common for a buyer to request an image where the subject can be clipped out, which means that in order to look right the person can't have pieces cropped off of his or her head, elbows, etc. Just missing a little bit of the subject off one side of the frame doesn't make the composition any stronger and it can definitely lose a potential sale if the buyer needs to clip out the subject.

© Blend Images/Andersen Ross/drr.net

Of course unless you're shooting completely full figure there has to a somewhat of a crop, but it should be confined to just the bottom of the frame so that the rest of the subject is clean. Like this:

© Blend Images/Andersen Ross/drr.net

So a good rule of thumb is either crop powerfully or not at all.

Finally, if the image is composed to allow for clipping, be sure your keywords make it easy to find. "Cutout" is the most common term, and "white background" or "plain background" are also useful.