I am 介绍自己的身份 . I will/am与请求有关的自身现状. I’d like to阐明自己的请求 . I will appreciate your有关该请求的详细信息 . I’m going to对方如能帮助实现请求，自己将要做什么 。
Here are the reasons why承上启下，开始解释原因 : For one thing请求的原因一; For another请求的原因二, .Therefore,总结写信的目的 .
I shall be much obliged to you if you对收信人的期望 . Thanks for your kind consideration and I look forward to receiving your earliest reply.
Dear Sir or Madam,
I am a senior university student majoring in vehicle engineering. I will/am going to attend an English test in the near future. I’d like to buy a reference book entitled Simulated English Test paper for Postgraduate Qualifications. I will appreciate it if you would help me find one and mail it to me . I’m going to refer to it intensively to improve my English.
Here are the reasons why I am in so desperate of the book: For one thing,I am busy preparing for the postgraduate examination, which is scheduled in December; For another, the book is written by a lot of famous and experienced professors. Therefore, I write to you here to apply for the book.
I shall be much obliged if you can let me have this book by the end of this month. Thanks for your kind consideration and I look forward to receiving your earliest reply.