Using the best tools for the job
In Web design, certain tools are essential. You need a WYSIWYG HTML editor. I don't really believe that graphic designers can produce a decent page using a pure text editor only. There are plenty of products to choose from at a variety of price points with varying emphasis on layout accuracy and code efficiency.
You also have to have a good Web graphics program. The ubiquitous Adobe Photoshop may be good for creating images, but it isn't the best tool for optimising Web graphics. Here, you will need a more specialist Web graphics tool like Adobe ImageReady, Macromedia Fireworks or Ignite from Ben Summers. There are also a number of Photoshop plug-ins from companies like BoxTop that extend Photoshop's capabilities.
The one single thing that I find most beneficial for Web graphics design is Bob Stein's VisiBone Web Palette. Instead of having to choose colors from a swatch or palette that is ordered by index for the computer's convenience, Bob has sorted the Web-safe colors by hue, and arranged them so that you can judge the individual colours without the false perceptions you get from the juxtaposition of similar colors in a row.