How to be polite in English 

用 I 代替 You

Your room is a mess

I think your room is a mess

用問句取代祈使句

祈使句：使用原形動詞使開頭的句子 (點餐、問路、買東西)

Can you go clean your room

使用正面詞彙

I think your room is a mess

I think your room is not very well organized

This food is bad

This food is not good

使用過去式

Can you go clean your room

Could you go clean your room

Would you like something to drink

句子加上 Please

Could you go clean your room

Could you please go clean your room