1. 先说格式吧。一般用的是缩进式和齐头式。
（1）缩进式
算是传统的英式结构。称呼顶格，每段第一行向里缩进4-8个字符。落款在中间偏右。
Dear Jason,
I'm so glad to hear from you. How have you been these days?
In your last letter, you talked about movies you love. I agreed with you that Life of Pi is a great movie.
Anyway, here is one of favorite movies that I would like to recommend to you.......
Yours,
Li Lei
(2)齐头式
美式结构，一般商务英语，电子邮件都会用到。称呼，段落，落款都顶格，段与段间空一行。
Dear Jason,
I'm so glad to hear from you. How have you been these days?
In your last letter, you talked about movies you love. I agreed with you that Life of Pi is a great movie.
Anyway, here is one of favorite movies that I would like to recommend to you.......
Yours,
Li Lei
2.结构
包括信头（寄信者地址和寄信日期），收信人地址，称呼，正文，结束语，签名。有时还有附言，附件什么的。
No.5, Qingtai Road
Hangzhou, 310000 信头
P.R.China
Dec.13, 2012
Doctor Jason Mraz
15 Linkin Avenue 信内地址
San Francisco
California 31000
U.S.A
Dear Dr Jason, 称呼
I'm so glad to hear from you.
....... 正文
......
Yours sincerely, 结束语
Li Lei 签名
P.S.:...... 附言
3. 称呼 一般都是Dear+人名，
（1）私信
关系亲密的话就直接"Dear+人名（Dear Jason,) ". 关系不很亲密的话就要用"Dear+姓（Dear Mr. Smith,)".女性不知道是否结婚的时候就用"Ms."
(2) 公信
收信人头衔+姓/全名
不知道姓名的时候可以用：Dear Sir or Madam, To Who It May Concern
4.正文 一般是三段式的
（1）说明为什么写信。写给不认识的人要加上自我介绍。回信的话要提下收到上封信的时间，和上封信的内容。
（2）最主要的部分。展开问题，讨论重要内容
（3）结尾。客套下： I am looking forward to your reply.
5. 结束语
1.万能的用法是：Yours sincerely, 或 Sincerely yours, 最方便，什么信件都适用哦。
2.私人信件中可以用：Best wishes, Best regards, Best, Regards, Warmesr regards, Yours ever, Yours, Cordially
3.一些很亲密的亲人或者朋友可以用：Affectionately, Yours affectionately, Love, Lovely, Cheers, Your devoted friend, Your loving father (mother, son......)
4.公务信件的话，一般可以用：Yours faithfully, Yours trully, Yours respectfully, Yours gratefully, Yours cordially
如果是公务的正式信件中，给团体或者不知名的人写信，还可以用：Trully yours, Faithfully yours
6. 签名
基本上就是这样了。可能还有附言，便签，备忘录什么的，不过不太常用。