The purpose of the cover letter is to tell the editor why your article should be published in their journal. Consider using the following template, and be careful to keep it short (1 page) and simple!
I am writing to submit a manuscript entitled [Manuscript title] for publication as a [Article type] in [Journal mame].
[Explain why your manuscript is important or novel and why it would be interesting to the journal's readership. Tell the "story" in a compelling way. Don't exaggerate. Don't use jargon or get bogged down in technical details. Don't copy text vertabim from your manuscript].
[Provide any information specifically requested by the journal (e.g., conflicts of interest, whether the manuscript is currently under consideration at other journal, etc.]
Thank you for considering our manuscript for publication in [Journal name]. I look forward to your response.
[Your name and contact information]"
Many journals ask for a list of potential peer reviewers for your article.
DO suggest researchers who you frequently cite in your article.
DO suggest researchers with whom you have had positive interactions with in the past, such as during a conference poster session.
DON'T suggest personal friends, close collegues (i.e., people with whom you've published in the last 5 years), former supervisors, or indviduals who have previously read and provided feedback on your article.
DON'T suggest only the biggest names in your field.
Keep in mind that the journal editor may not follow your suggestions. They may choose not to send your article to a reviewer who is notoriously slow, brash, or does not provide solid reasoning behind his/her criticisms.
Some journals may also ask for a list of individuals who should NOT review your article. These might be researchers who have strong, opposing viewpoints or individuals with whom you have had negative interactions with in the past. Be sure to keep this list relatively short.