投诉信通常包括以下几个方面的内容：说明投诉的原因并表示遗憾;实事求是地阐述问题发生的经过，切忌夸大其词;指出问题引起的后果;提出批评及处理意见，或敦促对方采取措施，或提出所希望的赔偿以及补救方式。

投诉信的写作策略：说明投诉问题——描述具体情况——期待解决方案。

注意事项：写投诉信时语气要冷静、郑重、克制，不必过于礼貌。但也要就事论事，不能进行人身攻击。同时，在描述问题时尽量采用被动句式，使描述更加客观合理。

投诉信开头常用句式和套话： 

I am writing to complain about/that...

I am writing to make a complaint about...

I am writing to express my concern/dissatisfaction/disappointment about...

I feel bad/sorry to trouble you but I am afraid I have to make a complaint about...

I am most reluctant to complain, but...

I am writhing to advise you that I find...unsatisfactory.

I wish to draw your attention to the problem/fault...that I bought...

It is with great reluctance that I must inform you that...

投诉信结尾常用句式和套话： 

I trust you will take my complains seriously and...

I will appreciate it very much if you could...

I would be perfectly satisfied if you can kindly...

I understand you will give immediate attention to this matter.

I would like to have this matter settled by the end of...

Frankly speaking, I am not prepared to put up with the situation any more.

I must have you fully understand that without a satisfying solution, I will reserve my right to take legal action.

I would be grateful if you could...

I would appreciate it if you could...