Your cover letter’s primary role is to encourage interest in you from a recruitment agency or employer; but does not replace your resume.
The cover letter should be a document that briefly indicates your suitability to the advertised position and encourage the reader to refer to your résumé for additional detailed information.
The worst way to get the reader’s attention is to spell his/her name incorrectly. A salutation that inaccurately reflects the readers gender is also not good. If you are responding to an advertisement that contains a contact name, use the name correctly. If in doubt, phone the company. Receptionists are a great source of information.
Be cautious when using “form letters” for your cover letter. Correctly addressing a letter to “Mr. John Smith” is undermined if your letter also starts “Dear Sir/Madam” or refers to a job advertised by another company.
Don’t try to oversell yourself in the arrogant style sometimes suggested by “self-help” books. Just because overselling helped the author sell their book, does not automatically mean that overselling will have the same effect on your resume. Most Australian employers value quiet confidence and honesty.
State why you think you are suited to the position that you are applying for. Highlight specific relevant experience but do not over do specific experiences. The detail should be on your resume.
Make sure you include your current contact details in your cover letter. This sounds obvious but does not always happen!
Finally, do not get discouraged. You can not please everyone and at the end of the day, your resume will be assessed by a human being who has individual likes and dislikes that you can not possibly predict.