An excellently written covering letter will ensure your CV is at least glanced at.  Keep it short.  Avoid colour and exhuberant formatting.  And, pay attention to the following, crucial elements:

Addresses

• Include your address first, followed by the name, title and address of the person you are writing to.  Pay attention to the details.  Do not spell names incorrectly.  (You know how annoyed people get about that?)  Make sure you have the correct postcode.  (Look up postcodes with Royal Mail or addresses with PostcodeAnywhere.)
• Punctuation in addresses in letters like this is optional, in the sense that it is no longer required.  My advice is to avoid using it, in order to avoid using it inconsistently.
• Use one or two spaces to separate out the addresses, from the date and the date from the salutation and so on…

Date

• Do not neglect to include the date.  (This is a very common mistake.)  Use whichever format you prefer.  Wednesday, 14th July 2009 and 14/07/09 are both fine, for example.
• Leave one clear, paragraph space below the date.

Salutation and Signoff

• Dear John/Mr John Bartholemew is paired with Yours sincerely (Where you do you the name of the person you are writing to.)  It is entirely acceptable to drop the traditional comma following Dear Sir/Mr Bartholemew.
• Dear Sir is paired with Yours faithfully (Where you don’t know the name of the person you are writing to.)
• Leave one clear, paragraph space below the salutation and sign-off.

Opening and Closing Paragraph

State the reason for the letter.

• With reference to your advertisement for a Personal Assistant/Senior Developer/Part-time Accountant…

Make a call to action at the close.

• Please let me know if you think my CV matches your requirements.
• Please contact me to arrange a meeting to discuss the openings/possibilities.

Main Body

State why you think you’d be a good match for the job.

• Highlight – rather than list – your major achievements in previous positions.
• Highlight your most relevant qualifications.
• Two or three short paragraphs (two to three sentences each) should be sufficient.  Avoid using a second page.
• Use one paragraph between paragraphs.
• Avoid indented paragraphs; they are outdated.

Spelling and Grammar

• Do not make mistakes in this area.  It makes your letter difficult to read, and makes you seem unprofessional.
• If English is not your first language, then you must look it up or ask a professional friend (whose first language is English) to check it over for you.  We’ve received multiple CVs with this particular problem.  The English is so poor, we simply give up and discard the letters.

Better again, if you’re completely stuck and really can’t figure out where to begin, send in your CV and job description and we will do it for you.  You can then use this template to write additional covering letters for different types of posts.