In the friendly letter format, address, date of closure, signature and printed name bleeding in the right half of the page (which so far screenplay up to you, as long as the title and closing is aligned, use their own discretion and make sure it looks presentable). Also the first line of each paragraph is indented.
All that is needed is the street address on the first line and the city, state and zip code on the second line. (Not required if the letter is printed on letterhead already on it.)
Put the date on which the letter was written in the example format Month Day Year July 30, 2010. Skip a line between the date and salutation.
It usually starts with Dear so and so, or so and so Hi. Note: There is a comma after the end of the salutation (use an exclamation point also if there is a need for some emphasis).
The body is where you write the contents of the letter, the paragraphs should be single spaced with a skipped line between each paragraph. Skip 2 lines between the end and the closure body.
What is the reader to know that you are finished with your letter, usually ends with Sincerely, Sincerely, thank you, and so on. Note that there is a comma after the end of the closing and only the first word in the closing capital.
Your signature will go in this section, usually signed in black ink or blue pen. Skip a line after your signature and P.S.
If you want to add anything else to the letter you write a PS (Post Script) and the message after that. You can also add a PPS after the PPP and one after that and so on.