Giving And Responding To Opinions

In general, the purpose of cover letters is to interest prospective employers enough so they call to schedule an interview. To fulfill this purpose, you'll need to target each cover letter to a specific company and position, showing how your background and abilities fulfill particular company needs.
Generic letters written to prospective employers are not enough. Those hiring will see such general letters for what they are: they'll realize that you haven't invested much time or effort in researching their company and writing an individual letter. And they probably won't invest their time by interviewing you.
You'll find that time spent to research the company, to determine how you're going to pique your readers' interest, and to write a letter convincing a prospective employer that your background matches company needs is well worth the effort.
Particular Purposes and Information
Cover letters are sales letter. Essentially, you're targeting your credentials to a particular market -- one company -- and persuading that company to make the buy. To fulfill this overall purpose, you'll need to achieve several goals in your letter:
Your letter should provide readers with some insight into you as an individual. Draft your letter in a way that shows how you as an individual will fit into the organization.
Use key terms from the ad or job description that are clearly relevant to your background.
Structure your letter so that each part achieves these particular goals:
In the opening paragraph of your letter, clarify your purpose in writing and build reader interest.
The body of your letter will need to persuade the reader that you have skills and abilities useful for the company.
The closing of your letter should request an interview as well as a strong reminder of the benefit to the prospective employer of scheduling an interview.