Asking Permission

When asking for permission to do something we usually use the word 'please' to make the request sound more polite. It is not grammatically necessary to use 'please' but you may sound rude if you don't use it. 'Please' can be put in different places in the sentence; at the start, end or before the verb:

Please can I borrow your pen?
Can I please borrow your pen?
Can I borrow your pen, please? 

A more important way of showing politeness is your tone of voice and intonation. Even if you use the word 'please' you can sound rude if your tone is not correct.

Generally the longer an expression is, the more formal and polite it sounds. However remember that a polite tone of voice is always very important in a spoken request for permission.

Below are some different sentence structures to help you form a polite request:

Question Head	Subject	Verb phrase with base infinitive
Can Could  May	I he we they	borrow this book? use your pen? take the day off? ask you a question?
Question Head	Subject	Verb phrase with present simple
Is it ok if Is it alright if	I  he we they	borrow/s this book? use/s your pen? take/s the day off? ask/s you a question?
Question Head	Subject	Verb phrase with past subjunctive
Would it be ok if Would it be alright if	I he we they	borrowed this book? used your pen? took the day off? asked you a question?

Source: http://www.bbc.co.uk/worldservice/learningenglish