写一封高三英文求助信时，你可以遵循以下结构和要点：

开头段

问候并自我介绍。

明确写信的目的。

正文

陈述具体的困难或求助事由。

可以分点详细说明，使内容条理清晰。

结尾段

表达期盼回复并表示感谢。

以下是一个求助信的示例：

Dear [称谓],

I am [你的名字], a Senior Three student from [你的学校]. I am writing to seek your help in [具体求助事由].

Now, I struggle a lot in [遇到的困难]. For one thing, [困难一]. For another, [困难二]. Therefore, could you please put forward some practical suggestions?

I would be grateful if you could provide any help you can. Thank you for your consideration.

Sincerely,

[你的名字]

示例解析：

开头段：

Dear [称谓], I am [你的名字], a Senior Three student from [你的学校]. I am writing to seek your help in [具体求助事由].

正文：

Now, I struggle a lot in [遇到的困难]. For one thing, [困难一]. For another, [困难二]. Therefore, could you please put forward some practical suggestions？

结尾段：

I would be grateful if you could provide any help you can. Thank you for your consideration.

建议：

保持礼貌：使用礼貌用语，如“I would be grateful if you could”和“Thank you for your consideration”。

具体详细：尽量详细说明你的困难和需要的帮助，以便对方更好地理解并提供有效的建议。

检查语法：确保语法正确，拼写准确，使信件看起来更加专业和正式。