Depending on how long you want your cover letter to be, the opening can be a single sentence or a paragraph in size. The opening has probably the hardest job of the cover letter, because it has to grab the readers’ attention, set the tone (which will convey a little about your personality) and the content for the remainder of the letter.
When responding to a job advertisement, you need to refer to the open position and the date and location where you saw the advertisement, unless of course, you already included this in the header section. Follow this with why you would be great in that position.
Examples:
In response to your advertisement for an administrative assistant in the Globe, October 12th, I am submitting my resume for your consideration. I have 15 years of experience working in a variety of industries and rise to the challenge of keeping order in chaos, being reliable and available, and make a positive impact on customers and vendors alike.
or
I’m a Business Analyst with 10 years experience in the commercial software industry, and it’s with great interest I’m enclosing my resume for the position of Senior Business Analyst featured in the Times on October 12th.
or
When I read your advertisement for a Head Chef in the November issue of the Cookmagic Magazine, I knew this was a position where I could excel, given my 5 years of experience, as a Sous Chef under the expert guidance of two of the top restaurateurs in Manhattan.