Cover Letter Greeting. The first rule of cover letter etiquette is to send a cover letter—always. Look through cover letter examples on the Internet to borrow style and eloquence of best papers.
Include these important sections in your cover letter: Heading and greeting. It doesn't matter if the hiring manager didn't ask for it or you're too busy to write one. It's a chance to demonstrate professionalism and even effort -- for instance, addressing your hiring manager by first and last name shows you did your research.
Even so, you should still be aware that your resume/CV is the main player, whereas the cover letter's role is a supporting one.
Including a professional cover letter salutation sets the proper tone of the rest of your cover letter and job application.
Here you can see the information in the "Quick Tips for Cover Letters" and "Preparing to Write a Cover Letter" pages put to use. A cover letter needs to be formal. If you can, have a friend proofread before you hit send, to pick up any typos or grammatical errors.