Could I know your name?
May I catch your name?
是很正确很温柔的问法,也可以在最后加个Please.
另外,What's your name?这种问法是长辈对年轻人,或者警察审问犯人时的语气问法,一般注重场合下是不会这样问的.
其实很简单,你就说
your name,please
Can you tell me your name?
Can you tell me what your name is?
May I have your name?
Should you tell me your name?