If we want to be polite we should follow some rules of writing letters.
We should remember of correct organization of the letter (its body). Мы должны помнить о: правильным построением письма (его структура), correct punctuation (правильной пунктуации), correct spelling (правильном написании слов).
You`ve got enough knowledge to write correctly, today let`s deal with the organization of the letter.
Look: when we write a letter to a foreign friend we start with a date. For example: the second of September. The next moment is greeting (приветствие).
Look: Dear Barbara. This is the greeting of our letter.
Then we have the body of the letter (what we write). To be polite and interesting for the person we write to, чтобы быть вежливыми и интересными человеку, которому мы пишем, we should start with something interesting about that person. Then, something good you noticed about him or her, after that we ask a question or some questions you want to ask.
In the end of the lesson we `ve got a closing. For example: your friend.
And we finish the letter with a signature or name. Look: your friend Dima.
Look at the example of the letter:
Here we`ve got the date in the beginning: 5th of October.
The greeting: Dear Barbara.
An interesting fact about the person: I was glad to hear that your stay in Russia was pleasant.
Something good about the person: I can say that you helped my English very much last year.
A question to the person: Are you going to come back to Russia?
A closing: Your former student.
And finally, the signature/ name: Dima Ivanov.