The modified block format is a widely used format, wherein the body of the letter and the addresses of the sender and recipient are single-spaced and left-justified, according to the Online Writing Lab of Purdue University. The author tabs to the center point for the date and closing.
For the return address, type the sender's name, address and phone number five spaces to the right of center, recommends About.com. Add the date five spaces to the right of center and around three lines below the letterhead.
Type special mailing notations and on-arrival notations in uppercase characters, if necessary. Include the name and address of the recipient four lines below the last typed line. Type Mr. or Ms. before the last name of the recipient to show respect in the salutation; however, avoid guessing the spelling or gender. Do not write the recipient's name when using an attention line to human resources. Common salutations include "Ladies," "Gentlemen," "Dear Sir," "Dear Sir or Madam" and "To Whom It May Concern."
The subject line is where you should write the gist of the letter in one concise line and in uppercase characters, notes About.com. Write the body of the letter briefly and straight to the point, maintaining two spaces between sentences. Center-align the complimentary close with the date, and align the signature block with the complimentary close.