Is a well-prepared resume enough to convince potential employers that  you should be called in for an interview? Don't be too sure. Not  including a cover letter with your resume -- even when you submitted it  online -- is passing up a key opportunity to sell your skills. 
A  recent nationwide survey by our company found that 60 percent of  executives believe the cover letter is either as important as or more  critical than the resume. A cover letter allows you to direct the  reader's attention to aspects of your resume that are most relevant,  demonstrate your knowledge of the company you're writing to and explain  any part of your work history that needs clarification. The following  guidelines can assist you in preparing a solid cover letter: 
Follow a standard business letter format.  Try to address the letter to a specific individual, even if it means  making several calls to determine his or her name and title. And be sure  to ask for the correct spelling. A prospective employer who sees his or  her name spelled incorrectly may assume you are not detail-oriented.  Once you've determined the hiring manager's name, a good general rule  for salutations is to use his or her first name only when you've been  personally introduced and have already referred to that person by first  name in conversation. Otherwise, use the person's surname preceded by  Mr. or Ms. If you are responding to a classified ad with a box number,  or if you're unable to obtain the spelling of the hiring manager's name,  use a greeting such as, "To Whom It May Concern." 
Writing the opening.  The opening sentence of a cover letter should announce its purpose  (even though the purpose may seem obvious) and give the reader a  compelling reason to read on. If someone mentioned the job opening to  you, be sure to use his or her name in the introduction: "I am writing  to you at the suggestion of John Doe, who told me you may be looking for  an office manager."If you're responding to an advertisement for a job,  say so in your letter: "I am applying for the marketing manager position  advertised in the Daily News and would like to tell you about my  qualifications." 
Demonstrate your knowledge of the company.  Work a fact or observation about the company that isn't common  knowledge into your opening paragraph. Such a statement tells the reader  you've done some homework: "I have been following with great interest  the success of your company in developing and marketing a line of satin  skirts. That interest has prompted me to send you this letter, along  with my resume." You could also say, "I am writing because I was taken  with your recent ad in the San Francisco Chronicle. In light of the work  your company is now beginning to do in gene splicing, I thought my  previous research fellowship in this area would make me a valuable  candidate for a position." 
Explain your current situation.  Are you finishing school or in a full-time job? Can you begin work  immediately or are you available upon completion of an internship?  Clarify these points in your cover letter. 
Explain why this job interests you.  Let potential employers know what you have to offer. Do you have any  special abilities or knowledge that you could build upon if hired? A  part-time job in college may have been in the same industry as the firm  you're applying with now. Or you may have experience with a specific  software application that will be used extensively in the position. On a  similar note, be sure to research prospective employers and demonstrate  that knowledge in your cover letter. Not only does this show that you  have a genuine interest in the job, but it also indicates that you have  initiative?a quality that is highly sought after in entry-level  candidates. 
Briefly elaborate on one or two key points to draw attention to your resume.  Give details about the most relevant parts of your work history for  this particular position. For example: "I served two terms as president  of ABC University's student golf club, where my responsibilities ranged  from overhauling the organization's fee structure to representing our  members in key meetings with faculty and other university leadership." 
Don't rehash your resume. The cover letter should generate interest in the resume, but not reiterate the same points. 
Have someone else review your cover letter.  While you may have used spelling and grammar checkers on your computer,  thoroughly proofread for any typos, poor grammar or spelling mistakes.  Ask a friend or family member to review it as well. Remember, potential  employers take cover letters very seriously, so be sure that you do,  too. 
Closing the letter. End the letter with Sincerely, Sincerely Yours, Yours truly or Cordially. 
How about electronic cover letters?  You still need a cover letter if you apply for a job via the Internet.  Online letters do not need to be as lengthy as traditional ones, but the  elements should remain the same. Use professional salutations such as  "Mr." and "Ms.," and always include your full name, telephone number and  mailing address. Appearances aside, what really matters in a cover  letter is what it says -- and that it generates enough interest to draw  people to your resume. Use the guidelines above to make sure what you  state in your letter delivers exactly the message you want to convey.
Source: careerbuilder