A cover letter is a short letter that accompanies your résumé and any other application documents that you send when applying for a vacancy or expressing interest in a work opportunities that may become become available in the future.
There is an abundance of advice that you can access through an internet search on how to write cover letters. Some useful web links appear below:
Youth Central on cover letters.
myfuture - select "Career Insight" and enter "cover letters" into the keyword search.
Sample cover letter - responding to an advertised vacancy. pdf format. Microsoft Word format. Rich Text format.
Sample cover letter - cold canvassing/cold calling cover letter. pdf format. Microsoft Word format. Rich Text format.