Write your letter, including the salutation and the body of your missive.
End your letter with a polite phrase. This can be the standard "Yours faithfully," or something more elaborate. Consider the audience. A formal letter should carry a formal closing, while a letter to a loved one may be more heartfelt.
Sign the letter below the closing. You can write it in manuscript or in cursive. You can also add creativity by adding stylish underlines or flourishes of the pen.