写英语请求信时，可以遵循以下步骤和结构：

称呼

使用正式的称呼，如“Dear Mr./Ms. [Last Name],”或如果不知道对方姓名，“Dear Sir/Madam,”。

问候语

简短问候，如“Hello,”或“How are you？”。

正文

开头：简要说明写信的目的，例如，“I am writing to request…”（我写信是想请求……）。

中间：

说明请求的原因：详细阐述为什么需要对方的帮助或信息。

提供背景信息：如果适用，提供相关的背景信息以帮助对方理解请求的背景。

提出具体请求：清晰、明确地提出你的请求，例如，“Could you please provide me with some information on…？”（您能为我提供一些关于……的信息吗？）。

结尾：表示希望对方能够给予答复，例如，“I look forward to hearing from you.”（期待您的回复。）。

祝颂语

使用常见的祝颂语，如“Best regards,”或“Sincerely,”。

具名和日期

在信的最后，写上你的全名和日期，例如，“Sincerely, [Your Name] [Date]”。

示例：

请求信

Dear Mr. Smith,

I hope this letter finds you well. My name is John Doe, and I am a student at XYZ University. I am writing to request your assistance in preparing a research paper on climate change for our upcoming seminar.

As you know, climate change is a pressing issue that affects us all, and I believe that your expertise in this field would greatly contribute to the quality of our discussion. I am particularly interested in your insights on the recent policies and initiatives aimed at combating climate change.

Could you please share some of your recent publications or presentations on this topic？ Additionally, if there are any specific resources or contacts you would recommend, I would be grateful for your assistance in obtaining them.

I am looking forward to your response and hope to schedule a meeting to discuss this further. Thank you for considering my request.

Best regards,

John Doe

[Date]

通过遵循上述结构和步骤，你可以撰写一封清晰、礼貌且有效的英语请求信。