留学生在交流时，可以使用以下几种表达方式：

问候和自我介绍

问候：Hi/Hello/Hey, how are you？/How's it going？/What's up？

回答：I'm good/fine/OK, thanks. And you？

自我介绍：Hello, my name is [Your Name], I come from [Your Country], and I am currently studying [Your Major] at [Your School].

表达感谢

谢谢你[帮助你的人的名字]， 我很感激你的帮助。

表达紧急

ASAP （As soon as possible）

表达原因

BC/cuz （because 的缩写）

顺便一提

BTW （By the way）

表达知识分子特质

We should stand firm and not compromise our principles.

We should contribute to our country and society with our knowledge and skills.

表达期待和承诺

I'm looking forward to this new adventure and the opportunities it will bring.

I promise to give my best in my studies and return to serve my country.

这些表达方式可以帮助留学生在海外更好地融入当地文化，同时也能够表达他们的情感和想法。