The Basics:

1. From Name:  Who are you?  Your recipients need to be able to recognize this in that instant when they are deciding whether or not the message is from a friend or from another company trying to sell them something they don’t want.  Does your company dominate your image, or do you?  If you run a small business, your personal name may be a better choice than your company’s.  If you aren’t sure, send half of one campaign using one name, and the other half using the other.  See how many messages are opened from each group.  Your recipients will tell you who they think you are.
2. Subject: This is your first impression.  A lousy subject line can turn a meticulously designed message into a complete waste of time.  Make a list of the most interesting and trust-inspiring lines you can think of – if you can, ask a friend to judge how interesting and non-spammy they think they are.  Narrow your choices to two or three, and send each to 10% of your contact list.  See how many messages are opened.  The top performing one is your subject line for the remaining 70-80% of your contact list.
3. Pre-Header: If you are using a pre-header, be sure it reflects the subject line.  It should not repeat the subject line, but it should expound on it (yet still stand on its own as a second subject line).  If your preheader is a completely new subject, your viewers are going to get a slightly dischordant vibe, reducing their confidence about the message to follow.
4. Headline: Keep the headline short, honest, and accurate.  Don’t be seduced into using flowery excessive “hot words” if they don’t accurately reflect exactly what your message is about.

The Details:

1. Your Appeal: What is your reader getting our of reading this?  If you consistently offer deals, entertainment, or something extremely well written, your readers are going to remember your name.  If you don’t give something of value to your readers, they are going to remember you for that.
2. Your Wording: Getting a message written and sent quickly saves time, but don’t forget to make sure your wording makes sense and sends the most effective version of what you are trying to say.  Avoid statements that can be interpreted in two ways – even if both ways seem to work.  If you have an ambiguous line in your copy, don’t fix it – replace it.
3. Text or Buttons for Links: People like clicking buttons more than text.  That is just a fact.  If you use a button, you are potentially sending an ugly line of code or a broken image, though.  Services like MailChimp, Constant Contact, AWeber, and Vertical Response can increase the likelihood that images will load in your email, but be sure to create alternate (alt) text for every image appearing in your message.  If you aren’t using a service, you may find that buttons just aren’t a good idea – few people will have their images load automatically.
4. Placement of Call to Action: Placement is an art more than a science.  The most effective placement should be based on length of letter, demographic, location of compelling statements, and even something as vague as the time of day.  Your goal is to cover as many bases as you can without loading the email with enough links to send your audience’s spam filters off.  Limit it to one or two conspicuous locations where the reader can quickly find it when they are ready to act.
5. Images: Images are more engaging than straight text.  The issue with images is the same as for buttons.  Your viewers may not be able to see them without taking another step and loading them.  In fact, most of your audience will not see them when they initially open the email, though they may see some very unattractive code or broken image icons floating all over the page.  If you are using a service to send out your email (and you should), you can consider using images, but if not, keep it simple and skip the graphics.
6. Testimonials: Testimonials appeal to emotional logic.  They can be very effective, but they can also take up a lot of space.  When you are writing your message, don’t capitalize on your audience’s time.  Try using testimonials, but don’t rely on them for every campaign.