In addition to what @Caleb has said, it is best that the background color and brightness that you use is similar to what you will eventually use in the final image. This is especially important if the object doesn't have sharp, straight edges, where masking may be difficult or time-consuming to perfect.
This is because when you extract your image off the original background, you will inevitably retain some of the background. Even a few pixels of a bright, white background will be very obvious if your product is then placed on a dark background (or if your final image has a transparent background and is rendered on a website with a dark background).
Generally it's easiest if you have a bright, white blown-out background. Very easy to select. But very troublesome if you eventually want to display on anything but white.