Sender Information First
Create a centered letterhead on your business letter that includes, on separate lines, your name, address, city, state and ZIP code as well as your email address if you wish. Since this information is supposed to stand out, use a font size slightly larger than that in your letter, or about 12 points. Alternatively, include this information at the very top of the letter. Format your letter in several ways -- block, modified block and semi-block -- but block format is the most common and the easiest on the eyes. Block format calls for a letter to be left-justified and single-spaced with a double space between paragraphs.
Write the date and then double-space. On separate lines, type: the company name, company address, company city, state and ZIP code. Double-space and write the attention line. Type: “Attention:” and the person's name or department to which you wish to direct your letter. For example, you might write, “Attention: Leon Smith, Accounting Manager” if you know the person's name and title or simply, “Attention: Accounting Manager” if you don't know the person by name. Double-space again and write a salutation.
Word of Caution
Some people abbreviate the attention line by writing "ATTN:" Since this is not a common abbreviation, spell out the word. You are writing the attention line to ensure that your letter arrives in the proper hands; don't risk using an abbreviation that might unwittingly foil your best intentions.