Write specific subject lines. A specific subject line can help readers understand what action they're to take with the email and can help them determine if that email requires immediate action. A good subject line helps readers, consequently benefitting you, because you don't have to open the email to find out what it contains.
Make your subject lines "actionable." If you need your readers to take a specific action, tell them what that action is in the subject line. For instance, if you have two questions that you need your reader to answer, a good subject line might be "Two questions that need answered." Of course, you can always tell them how quickly that action needs to be taken.
Get to the point quickly. Readers expect that emails will be brief and therefore, that they will get to the point. Unless your reader needs a lot of background information, get to the point early. Try one of these tried and true email opening lines.
Plan. Too many writers fail to plan their emails. We're not talking about an email in which you ask a colleague to lunch, but if you use emails to communicate with clients or others about your business, planning is crucial.
Email is not a substitute for conversation. Because email makes communicating quick and easy, we can often get caught up in pretending that it's conversation, but it's not. It's a written medium and therefore should be approached the same way we tackle other business documents.
For many businesses, email is the primary method for communicating; as such, it care should be taken to ensure that it conveys the appropriate message. If it doesn't, your business could suffer.