While your CV tells the employer about you, the letter should concentrate on the position and the company. Remember to fully research the firm, perhaps by visiting its web site, and use this information to help draft your letter.

The covering letter is your first contact with a potential future employer and a great chance to market your skills:

Do:

Include a personalised covering letter with every CV you send out.
Keep it short and factual - four or five paragraphs on one side of A4 paper.
Tell the recruiter where you saw the ad and include any reference numbers.
Refer to the CV you have attached - it might go missing and they'll think you haven't sent one.
Tailor it to each specific application - outline how your experience matches job requirements.
Say why you want the job.
Concentrate on telling employers why you would be good for the job, rather than why the job would be good for you.
If the job is in a different sector from the one to which you have devoted the past ten working years, draw links between the two.
Try and show that you have done some research into the organisation already - for example mention that you have read the latest annual report or visited their web site. Let hjobs help you with your research
Include any dates when you might be unavailable for interview. If you are able to take calls during the day, then provide a contact number.
Check that you have addressed your letter to the right person, that you have used the correct job title and spelt his or her name correctly.
You may wish to state your current salary and your salary expectations for the job. Use hjobs' salary checker for help.

Don't:

Simply send out standard covering letters to different employers
Underestimate the value of the covering letter - you can use it to lift your CV if your experience is lacking by drawing attention to your strengths.
Speculative letters.

If you are not replying to an advertised position, it may be worth writing a speculative letter to a company that you would like to work for. In this instance, begin by stating the specific work you are seeking, say why you want to work for this particular company and ask for your CV to be held on file for any vacancies that may come up.