Separating your subject from the background is a great way to increase to popularity of your image. if you will browse through the images at bigstockphoto you will notice that there are allot of images that are just subject and all the background is white. The way to get to good subject to background separation has two steps (1) have a good lighting setup and (2) use photoshop or similar software to post process your images.
Some of the micro stock image sites will even let you upload the clipping path that you used to isolate your subject.
here is a great article about using photoshop's pen tool to isolate your subject, and here is another easier way to use the extractor filter to do the same job on less complicated images.