While there is some variation, a typical cover letter is often made up of specific sections. See descriptions of typical cover letter sections below:

Contact Information
The first section of a cover letter contains your contact information and the contact information for the prospective employer. This section also includes the date that the cover letter was written. Below the contact information you can also include a reference line that lists the job title and number for which you are applying.
Salutation
This is where you greet the prospective employer. Begin with Dear. Use the appropriate formal prefix (such as Mr., Ms., Dr.) of the prospective employer followed by their last name. When addressing women who do not have a specialized prefix (Dr., Rev., etc.) it is generally best to use "Ms." unless you know that she goes by "Miss" or "Mrs."
Body of the letter
The body of the letter is typically broken up into three paragraphs.
Paragraph 1
This paragraph tells employers the purpose of your letter. If you are applying for a job, this paragraph should explain which position you are seeking. You can also use this paragraph to impress the employer with some knowledge about the company.
Paragraph 2
This paragraph tells employers more about you. It should explain why you are the best match for the position. It should summarize your qualifications and entice the employer to read your resume. If you need to clarify any information on your resume, that can be done in this paragraph as well.
Paragraph 3
This paragraph is where you wrap up the body of your letter. It thanks employers for their time. It also tells them how they can reach you or when you will be contacting them. If you want the employer to contact you, you can also remind them of your phone number or email address in this paragraph for their convenience.
Closing
This section should begin with a formal close, such as "sincerely." If you are mailing or faxing the cover letter, you should include a hand-written signature with your name typed underneath. If your cover letter is an email with a resume attachment, you can type your name for the signature.
You will also want to let the employer know that your resume is enclosed or attached. Below the signature line you will write "enclosure" if you are mailing your cover letter and resume. Write "attachment" if your cover letter is an email and you are attaching your resume. If you have attached or enclosed multiple documents, write the number of documents enclosed or attached in parentheses beside the word "attachment" or "enclosure." If you prefer, you can write the name of the documents you have included.
In addition to reading this article, look for an example of a formal business letter to see how the final product should look. Business-letter writing examples can be found in books on writing and on the Internet.

