A cover letter is a very important document that accompanies your resume, something that makes the employer consider your resume and application. It is very important that you draft it well and present it beautifully, so that it instantly attracts the attention of the prospective employer.
A good cover letter is one that does not waste time summarizing your resume but instead dwells on your suitability for the position. When writing a good cover letter you should ensure that it is addressed to the right person and includes his or her name in the salutation. The first part of a good cover letter should expressly state your interest in the position and also your reason for applying. You could mention the person who referred you or could mention the details of the advertisement, whichever is applicable.
The second part is the most important part of the cover letter, as it is where you can go beyond all boundaries and sell yourself. However, care should be taken not to exaggerate and overstate your abilities. Your abilities and experience should be stated simply and clearly, so that it enables the employer to take a decision.
Finally, the third part is where you thank the person for considering the application and reading the letter. Here you should also mention details about follow up. In other words you could give your phone number or could just state that you will call up the office and follow it up.