Cover letters should be attached to any professional job (desk jobs), any posting that specifically asks for one, and as a fax cover sheet.
Some text from Viriginia Tech’s Cover Letters web site: http://www.career.vt.edu/JOBSEARC/coversamples.htm and the MIT cover letters document: http://web.mit.edu/career/www/guide/coverletters.pdf
If you’re optimistic, make sure to use positive words, but don’t gush or get too excited about a position you love.
“As requested, I have included a writing sample – an article from my school newspaper, the State News, about the school’s annual volunteer day.” “Included is a recommendation letter from my high school counselor, Mrs. Jane Smith, whom I have known for ten years.”
This is not always necessary; if the posting specifies a certain date they will be contacting applicants, or if you’re just sending a resume to inquire, you don’t need to include this.
Your address comes first, then the date, then the address it’s being sent to. Always try to get the name of the person you’re sending to; “Hiring Manager” or “Human Resources” might sometimes get screened out. Microsoft Word’s Letter Wizard will do this for you, but be prepared to do it yourself, correctly.
It’s okay to just type whatever you can think of. Your first try will not be your only try. You can edit!
Text of example letter from VT Cover Letters site. (always leave a space between the end of the letter and your typed name, and sign your name in handwriting there.