Plain white photocopier paper is fine. It’s OK to print your letter on expensive cream or pale blue paper, but content and layout are far more important! Use the same colour for your CV. Don’t use lined paper or paper with punched holes!
If emailed put your covering letter in the body of the email. If you attach it with nothing in the email body it may be misidentified as spam.
Don’t make the employer work to read your letter! Keep it clear, concise and to the point.
Try not to go over one side of A4: if it does, you are writing an essay instead!
Use your own words not formal long-winded clichés.
Action verbs can help to make it sound better.
Spell-check and then double-check your spelling and grammar. Spell checkers won’t pick up form instead of from or sex instead of six!
Answer the question “Why should I see you?”
Make the person who reads it feel special: that it is addressed to them personally and not one of fifty identical letters you are sending out without thought or care,
You might include your understanding of the work/knowledge of the company, and how you fit the criteria required. “I have a real interest in working as a ….” will not do: you must say why you decided to pursue this career, what first brought it to your attention, why you as a History student should be interested in a career in finance.
Relate your skills to the job. Show the employer that you have obtained the communicating, teamwork, problem solving and leadership or other skills that are appropriate for the job.
Say when you’re available to start work (and end, if it’s a placement): be as flexible as possible.
Try to find the name of the person to write to. Research by Forum3 found that those who included a letter with their CV were 10% more likely to receive a reply and those who addressed the covering letter and envelope to the correct named person were 15% more likely to receive a letter of acknowledgement and 5% more likely to gain an interview. They also found that 60% of CVs are mailed to the wrong person, with the managing director being the main beneficiary of the unsolicited mail.
The above information was taken from the careers department of the University of Kent website.