Formats vary, of course, but the format that I was taught (many years ago, shortly after the arrival of the Nina, Pinta and Santa Maria

) for a standard business letter (snail-mail type, not email) was as follows:
Date
(enough vertical spaces so that your letter will be centered on the page)
Mr. John Doe
ABC Company
123 Sesame Street
Boston, MA 02134
<------- (two vertical spaces)
RE: YOUR JOB APPLICATION ADVERTISEMENT
<------- (two vertical spaces)
Dear Mr. Doe:
<------- (two vertical spaces)
text text text
text text text
<------- (two vertical spaces)
Sincerely,
IainC
