In designing the visual aspects of the letter, pay attention to

• Margins
  While traditionally margins are set to 1 in. on all sides, if you do not have much text, you may want to modify the margins so that your text fits somewhat symetrically on the page.
• Headings
  Use headings within a longer letter to guide the reader
• Stationery
  Use letterhead for the first page and plain or non-letterhead matching paper for additional pages
• Typeface
  Type the letter in a standard business font (Times, Garamond, Arial, etc.)
• Line Spacing

While single line spacing is traditional, your goal is to create a readable document; in some cases, depending on your font size and the quantity of text, 1.5 spacing may be more appropriate. Try various combinations and find the one that looks best.