Expert says never send your resume without a proper cover letter. In the cover letter, you have the chance to state why you are sending your resume to this company and for what specific position. Don't make people guess as to why you have sent them your resume -- make it clear right up front.
Write the letter to a specific person-the person you think is the one who would hire you. Do some research to find out the name of the person who will be reviewing your resume. This reinforces that this is not a generic cover letter, but one made especially for them.
Modify your cover letter to the particular job you are applying for and illustrate why you are the best choice for this particular position. Recruitment Managers look for specialized cover letters, not mass-produced ones.
Do research on the company you are applying for. Discuss why this company/organization appeals to you. This shows employers you went the extra mile to learn about them - it may give you the edge over the competition. Such information can be found on web sites, in annual reports, in your local newspaper and/or business journal, in trade magazines, etc.
Don't just repeat your resume. This is a chance to not only to illustrate your outstanding qualities, but to show your personality as well. Employers should want to meet you, not just your credentials.
Tell the reader what you can do for the company, not what you want the company to do for you. Please state some specific way in which you can add value to the company or department accomplish a particular goal, preferably giving an outstanding example of a related accomplishment
Mention only accomplishments that directly relate to the job you want to get. Your numbers can be approximations, so long as you can explain their rationale if requested. Think of quantifications involving estimated cost savings, contribution to a company's bottom line, employee retention, specific initiatives, etc.
Keep it brief, succinct and simple. Remember, you are trying to capture the reader's interest in knowing more about you. Please don't narrate your life story.
Make it easy on the eyes. When you've finished writing your letter, print it up and take a "big picture" look at it. Is it visually appealing? Does it look like a letter you would want to read?
Close with an invitation for the reader to act. Please tell the reader you would like to talk or meet at mutually convenient time and date.
Double and triple check for spelling or grammatical errors.
Follow up with a phone call-or a second letter-within a week. People get busy. They intend to call but get sidetracked by other priorities. Don't assume that someone isn't interested just because s/he doesn't call you after your first letter. So give the person a call if possible; if you can't reach him or her, write a second cover letter reminding the reader of your first letter.