Recruiters can get a pretty good sense of your background by scanning a well written resume. However, it's a simple no brainer cover letter that really puts your resume in context for the specific job with a specific company.  Your cover letter doesn't have to be  complicated or complex to do this. The role of your cover letter is to just focus the recruiter's attention by adding your personal voice to your resume.

Cover letter header should match resume header

With a simple cut and paste you can amp up the professional look of your resume and cover letter. Using the same header on both documents will look like you have your own personal letter head.

Cover letter opening statement should say how you learned about the job

Recruiters want to know how you found the job.  A simple statement in the opening sentence of the letter will achieve this. If you were referred by someone specific, this is a good place to share that information.

Refer to your resume & highlight specifics in cover letter

The second paragraph in the cover letter is where you connect your skill set, education and work experience to the specific job. Just identify the top three, most relevant, things you want the recruiter to know about you, relevant to that job. These three bullet points will strategically end up in the middle of your document and will be easy to read.

Use the company name at least 3 times in the cover letter

Although you are keeping the cover letter simple, you still want to strategically connect with the company. One way to do that in a cover letter is to mention the company name 3 places - in the salutatory address information, in the opening paragraph and in the closing paragraph.

Avoid "To Whom it May Concern" in cover letter

Remember that your goal is to get more "personal" in the cover letter than you can in the resume. Therefore, address your letter to someone specific. A little company research will usually get you the name of a specific person to whom you can address your cover letter. If after doing your company research you do not have a hiring manager's name, find the name of the Director of Human Resources. If all your research fails, use 'Dear Hiring Manager."

Closing a cover letter

No matter how simple you make the cover letter, the closing must be strong. It is perfectly legitimate to close your cover letter by stating your plan to follow up with the company if you do not hear a response by a certain time. Include your email and phone number right there in the closing section of your cover letter.  Don't let the employer have to look for it.