Every week or every month you put together your email. You know how it looks, you know the quirks of the layout, and you know how much copy looks good in it. But when was the last time you looked at it? Really looked at it? When was the last time you asked yourself, "Would I want to read this?"
Keep your layout clean and simple. If your web site has a distinctive feel to it, try to incorporate some of that into your email. Web sites, by necessity, have to achieve more functionality, while your email is about conveying your current offer or your current news; But don't just copy and paste the code from your web site and make it an email! Take the main color scheme of your site and build an email around that, or use a simplified layout, based on your site. As an aside, make sure that the display code of your newsletter is valid. Invalid, or broken, markup code can also make your email look like spam to automatic filters. Use a good HTML tool, or hire someone that knows a lot of acronyms.
When you evaluate your newsletter, keep the things that matter. Focus on the content first, then decide how to make it look pretty. If you're not saying something that your List Members want to read, then a beautiful layout only helps so much.
Remember, the things that we see everyday become commonplace and we often take them for granted. Another viewpoint can reveal how things truly appear.