英语书信的开头可以根据具体情况选择不同的表达方式，以下是一些常见的书信开头表达：

问候语

How are you doing？

How is everything going？

How is life treating you？

I hope everything is all right.

I miss you very much.

表达收到来信的喜悦

I am glad to receive your letter.

I am very pleased to hear from you.

It has been a long time since we met.

I am looking forward to receiving your letter.

自我介绍

I am Li Hua, a 17-year-old boy currently studying in XXX middle school.

回应来信中的问题或请求

You asked me about （+problem question 等）, now let me give you some advice.

表达时间流逝

Time past cannot be called back again.

其他

Thank you in advance.

Please write to me as soon as possible.

Good luck | Best wishes.

根据书信的内容和目的，可以选择以上合适的开头表达，使书信显得更加自然和友好。例如，在写一封感谢信时，可以先表达收到来信的喜悦，然后再转入正题，表达对对方的感谢之情。在写一封邀请信时，可以先自我介绍，然后说明邀请的目的和细节。