When working with white or light grey objects the default checkered pattern that stands for the transparent background makes it quite difficult to see the edges of your elements. It's especially difficult to judge semitransparent areas. I've seen designers adding another locked layer below the working layers filled with a dark color. This is a good solution, except that it adds to the file size and needs to be switched on and off when saving your work with the transparent background as a gif or png.

There is a simple way to replace the light checkered background to a darker pattern or any flat color prefereably one that is not used in your artwork. Just open Preferences/ Transparency and Gamut and play around with the different settings. It only takes a few seconds and will help your work tremendously.

To further customize your working space and recolor the area around your canvas follow this trick.