请问

Think of 请问 as the polite flag you raise before asking a stranger for facts. Shop clerks, taxi drivers, teachers, and customer service all get it; that's its home turf. Text your roommate 请问明天有空吗 and you sound like a bank hotline reading a script. Natives keep it loose with 问你个事儿, 问一下, or a quick 诶. The politeness itself creates distance, so using it on close friends is like calling your brother 'sir'.

“问问题，要知道，
问老师，说“请问”。” (When asking questions, you need to know: ask the teacher, and say 'Excuse me'.)

English 'excuse me' covers two very different jobs, and Chinese splits them cleanly. 请问 asks for information: where something is, when it opens, how much it costs. 不好意思 handles the small apology that comes with a favor or a mild interruption. So 请问借我一支笔 makes natives picture a robot reciting the wrong script. For favors, use 不好意思，能借我一支笔吗？ — that's the line people actually say.

Real conversations add 一下 almost automatically: 请问一下，这个多少钱？ That soft 一下 makes you sound friendly instead of official. Textbooks teach the bare 请问 because it is the clean version, then learners hear 请问一下 everywhere and freeze. You can also say 想请问你一个问题 when you want to formally borrow someone's attention. Keep 请问 as the opener and treat 一下 as the everyday softener.