Here are some guidelines:
1. Include a feature, a benefit, and an advantage in the opening. This needs to be used in a subtle way, but in the opening you're really doing a small marketing job for this issue of your email newsletter. Highlight an article or two that are important, explain what you're providing the readers that they won't get elsewhere, and tell them what the benefit will be. A great example is something like "Nokia and Sprint announced second quarter earnings today. Learn what our Wireless Week experts say about the results, and what effect you can expect them to have on the industry at large."
2. Put the email newsletter in the context of your readers' day. This goes hand in hand with the last point. Your readers are busy, and if you can make a compelling case for why they should stop what they are doing and take a few minutes now to read your email newsletter, you'll get them in. We recommend editors reference important events, upcoming trade shows, or other things that say to the reader "You will find it worthwhile to stop and read this email newsletter now, because the information in it will help you stay on top of your business."
3. Keep it fresh. Don't craft a "perfect paragraph" and use it issue after issue after issue. One of the keys to success is to keep the copy fresh and highlight items in that issue of the email newsletter. If you use the same generic language repeatedly, people will stop reading it and it'll be a waste of your time.
4. Keep it short. This is critical. We recommend no more than two to three sentences -- just enough to get them interested and pull them in to read the rest of your email newsletter.
Try it out and see the results! This is just one of the simple things you can do to engage your reader and optimize your CTR.