Editor’s name: First of all, make sure you address the letter to the correct person. If you can find out the name of the Editor, e.g., from the journal website, then use it. Address the Editor by last name, e.g., “Dear Dr. White,” or
“Dear Professor Green.” If the journal website does not list the Editor’s title, try to find it by searching the internet. If you are not sure of the Editor’s name or title, address the letter to “Dear Editor” or “Dear Editor-in-Chief.” Do not use “Dear Sir”: it will not impress any female Editor (or many male Editors either).
Article title: Make sure the article title in your cover letter matches the title in the submitted version of the article. If you revise your article, revise your cover letter.
Journal title: Make sure you write the name of the journal correctly. If your article has been rejected and you re-submit to another journal, make sure that you change the name of the journal. You will be surprised how many authors get this wrong!
Article type: Indicate the type of article (Review article, Research paper, Short communication, etc.), and check that this matches the name of this article type on the journal website.
Research aim: What was the aim of your research? Were you trying to solve a problem? Prove a hypothesis? Follow up on an unexpected result in a previous article (yours or that of someone else)? Don’t assume the Editor knows the precise details of your field of study. Give very brief details of the background if necessary. Spell out any abbreviations, and give the full version of any species name. Does the aim of your research match the Aims and Scope of the journal? If this is not obvious, add a sentence to explain.
Research findings: What did you find out? Don’t exaggerate, but don’t go to the opposite extreme either. If you make it sound too insignificant, why would anyone want to read the article)?
Research impact: What is the significance of your results? What is new? What is interesting? Add something interesting so that the Editor wants to read your article, or send it out for review.
Keep it short: don’t repeat whole sections of your article.
Keep it accurate: (perfect grammar, with absolutely no spelling mistakes). Check, double-check, then check again. Then give it to a colleague to read. Does any data in the letter match the data in the article? If you mention a 10% increase in yield in the letter, and a 7% increase in the Abstract, the Editor will start to doubt your research.
Keep it consistent: Format your letter to match the formatting of the article. For example, if you use P for probability values in the article, don’t use p in the cover letter)
Journal-specific requirements: Check the journal submission instructions for any specific requirements, such as disclosure of interests or suggested reviewers. Check the Aims and Scope.