Briefly, effective email is email that is concise, skimmable, has a well designed subject, header, sidebar, table of contents, and a clear ask. The design should be simple for clear messaging. The use of a template is very helpful. Keep the tone casual and personal, and the information easily accessible. Critical information should be above the fold—the fold is the line where your email disappears, as if it were folded like a newspaper. Keep the email well formatted and well sectioned, employ short introductions, and maintain a regular delivery schedule.

Let's look at some of these elements individually.

Subject: The most important part of your email is the subject line, as it is the only thing your recipient is guaranteed to see, so make sure to write an engaging, targeted subject.

Header: A good header is also important. Include your organizational logo and tag line in the header, and make sure your header isn't so large it pushes critical information below the fold.

Sidebar: Use the sidebar to highlight important information, such as the “ask” (if you don't know what this is, see below.)

Table of contents: A good email will include a table of contents, which makes it easy for the reader to see in a glimpse the email's contents and decide which articles to read.

Ask: The ask is the call to action you are presenting to your readers. Make it easy to see the ask by using the sidebar and graphics. Make the ask specific.

You may also want to consider list segmentation. This involves sending a message to only those on your email list to whom you think the message is pertinent. This can reduce email fatigue.

Want more info? Follow this link to a blog post from our sister site, Social Source Commons, which covers some email best practices:

http://blog.socialsourcecommons.org/2011/09/are-your-emails-skim-or-2/