In our daily life, we usually use direct questions to ask for information we do not know. Direct questions are either yes or no questions such as "Are you married?" or information questions such as "Where do you live?"
It's OK to ask your friends or someone you know well direct questions, but such questions can seem unfriendly at times, especially when you are asking a stranger. For example, if you come up to someone and ask "What time is it?" or "Can you move?", he or she may refuse to help you. It is certainly right to ask questions in this way, but it's very common to make these kinds of questions more polite by adding "Excuse me" or "Pardon me" to begin your questions. "Excuse me, when does the bus leave?" or "Pardon me, may I sit here?" sounds more polite.
It's also possible to use "can" in more informal （非正式的） situations. In the past, people used" can" when asking for something, but only to speak about abilities. In the UK, some English teaching materials from Cambridge University come with the phrase （短语） "Can you lend me…" "Can I have...", etc. In the US, this form is still considered to be not true, especially for written English, and "May I have..." is better. Questions with "can" will sound more polite by using "could": "Pardon me, could you help me?"
"Would" can also be used to make questions more polite. "Would you let me borrow your pencil?" is also polite.
Another way of making direct questions more polite is to add "please" at the end of the questions, We can say "Could you help me, please?" But notice this, "please" should not appear at the beginning of the questions.
