以下内容译自 Scott E. Fahlman 在 quora 上的回答：
有的学生发来的套磁信中只有一个简单的开头 Dear Professor ，连具体的学校和项目名称都没有，也完全没有提到我的科研内容，更没有提到自己的兴趣或能力是否和科研项目相关，或者只是在官网上简单地找了几个相关的关键词就说对这个方向很感兴趣，但是这完全看不出来你有用心了解过我的研究方向或内容啊，甚至有时候说的关键词还是错的，根本就不是我的研究方向！
所以，如果一个学生真的想加入到我的团队，在发邮件之前， 至少应该花点时间了解一下我到底在做些什么研究，细节越多越好，可以查相关的论文。 这不仅仅是对教授的一种尊重，更是对自己的负责，只有你真正了解了教授的研究方向，你才能知道这些东西是不是你感兴趣的。
基于以上，我认为一份好的套磁信应该 直截了当地介绍自己的基本情况，然后重点说明自己的科研背景和对项目的了解、匹配程度，可以适当询问教授项目的具体情况。如果教授对你感兴趣，自然会回答你的问题或者询问你更多细节问题。 另外，教授是否回信大多取决于以下几种情况：教授有多忙，你有多优秀，你的英语表达能力，你有多么想为这个教授工作。 并且，套磁信尽量早点开始， 这样你可以有更多时间跟教授联系，如果在申请旺季开始，每天我的邮箱里会收到茫茫多的套磁信，恐怕能不能看到你的邮件都是问题。 最后，套磁并不能保证录取。 哪怕我很喜欢你，但是如果我当时没有项目资金再多雇一个人，或者出现了更好的候选人，那我也没办法要你。但是，如果我真的很欣赏你，也许我可以推荐你到其他教授或者其他项目那里。
How do I write the first email to a professor that may accept me as his graduate student?
I get a lot of letters of this type. Let me tell you what NOT to do.
The first contact should not be a spam letter – that is, a letter that you could easily have sent to 1000 faculty members worldwide, and probably did. Why should I spend more time answering your letter or reading your resume/CV than you spent writing the letter?
Often the letter is not even minimally customized. It is addressed to “Dear Professor” and does not mention the project name or the university, even though you think my work is wonderful and desperately want to work with me. The letter gives no indication that the writer has spent even a few minutes looking at the online materials related to my work. And then these hard-working people, so passionate about my work, go on to say that they want to work with me on “algorithms, data mining, software engineering, and computer vision” – not areas that I currently work in.
Often I throw these notes in the trash immediately, or respond with a canned message pointing to a web page with info about how to get into a CS graduate program at CMU and about the specific issues of joining my group. (In case you’re interested, see Page on cmu.edu.)
But once you send me that spam letter, there’s no point in then going online and finding out what I do. You’re already a loser.
So if you think that you really want to work with me as a graduate student, first take some time to find out what kind of research I really do. Then, if you have no experience or preparation in this area, get some. Read and think about my papers (and the essays on my blog), and some papers in related areas. Think about what you might be able to add to this, and what it will take to get up to speed. Do your homework. Then write me a brief letter, making specific reference to all of that.
Then maybe we can talk, and maybe something will come of it.
– Scott Fahlman
P.S. It occurs to me that there’s something else I should have said: Yes, you should know what the professor works on, and should know enough about the field to know whether this work really interests you, before you bother a busy professor at all.
But, given that, the best kind of first-contact is a letter one saying, “I’m a student in my X year of Y university. I’m interested in your work on X (be specific) and would like to learn more about it. Can you suggest the best way to do that?“ You may get a canned answer, but that’s just because we all get so many of these queries. Read that stuff or play with the code, think about it, and see if you are still really interested. Maybe follow up, asking a specific question or two about the work, or try some little project based on the professor’s work.
Whether the faculty member chooses to carry on such a correspondence depends on several things: how busy the professor is at that moment, how good you seem to be, whether there’s a communication problem, and whether you seem to be truly interested in his or her work. Don’t keep talking about how interested you are – prove it! And try not to be too much of a load.
I’ve had a few correspondences of this type, and in a couple of cases it has led to my supporting the student for admission to one of our graduate programs. It’s best to start this early, so that by the time the discussion gets around to graduate admissions, I have a very good idea of whether I would like you as a grad student. Even if I like you, this still might not happen – it depends on whether I have an opening (and funding) for a new student that year and how good the other candidates are – but this is by far the best way to get started. If I can’t take you on, at least you might learn something interesting, and maybe I can suggest other faculty or other programs that might be a good fit for you.