Most learners are taught one way to make a request in Korean: verb + -아/어 주세요, “please do it for me.” 문 좀 열어 주세요, please open the door. It is correct, and it is polite in form. It is also, more often than learners expect, a little too direct for the situation.
Korean has a range of request forms that run from blunt to very soft, and choosing among them is less about grammar than about who you are talking to and how big the favour is.
The ladder
해 줘 (hae jwo) = do it for me
반말 imperative. Friends, younger siblings, partners. Can sound demanding without 좀 or a soft tone.
해 줄래? (hae jullae) = will you do it for me?
반말, but phrased as a question about the other person’s willingness. Softer than 해 줘. This is the friendly default between close people.
해 주세요 (hae juseyo) = please do it
Polite form, but grammatically a command. Perfect for shops, restaurants, taxis, and anyone providing a service. 아메리카노 하나 주세요 is exactly right.
해 주실 수 있어요? (hae jusil su isseoyo) = could you do it?
Asking about ability rather than giving an instruction. Softer, good for favours.
해 주시겠어요? (hae jusigesseoyo) = would you do it?
More formal and courteous. Common in customer service, professional settings, and with strangers whose help you are asking for.
해 주실 수 있을까요? (hae jusil su isseulkkayo) = do you think you might be able to?
Very soft. Wondering aloud whether it is possible. Good for real favours to people above you.
Why 주세요 can be too much
주세요 is polite because of -세요. But the structure underneath is an instruction. In a service setting, where you are the customer and the request is expected, that is completely natural. Outside that setting, especially when you are asking someone senior to do something they do not have to do, it can sound like you are directing them.
A junior employee who emails a manager with 확인해 주세요 (please check this) is not being rude, exactly, but it reads as a little flat. 확인 부탁드립니다 (I’d appreciate your checking it) or 확인해 주실 수 있을까요? sounds more like a request and less like a task assignment. In workplace writing, 부탁드립니다 (I humbly request) is everywhere for this reason.
What 좀 does
Adding 좀 (jom) softens almost any request. 문 좀 열어 줘 is gentler than 문 열어 줘. There is a separate post here on 좀, which covers why it does not mean “a little” in this position. For requests, the short version is: if in doubt, add 좀.
-ㄹ래 vs -ㄹ래요
줄래? is the casual form. 줄래요? adds the polite ending, and it exists, but it is worth handling carefully.
-ㄹ래 asks about the listener’s will: do you want to? will you? Between equals that is friendly. Toward someone clearly above you, asking about their willingness can sound oddly familiar, and some speakers hear 해 줄래요? from a junior as slightly presumptuous. 해 주시겠어요? does the same job with the honorific -시- built in, which is why it is the safer choice upward.
Examples in context
사장님, 여기 물 좀 주세요 (sajangnim, yeogi mul jom juseyo) = excuse me, could we get some water?
At a restaurant. 주세요 is exactly right here.
혹시 사진 좀 찍어 주실 수 있을까요? (hoksi sajin jom jjigeo jusil su isseulkkayo) = would you mind taking a photo for us?
Asking a stranger at a tourist spot. 혹시 (by any chance) plus the softest form. This is a favour, and the grammar reflects it.
이것 좀 봐 줄래? (igeot jom bwa jullae) = can you take a look at this?
To a friend or a peer you are close with.
내일까지 보내 주시겠어요? (naeilkkaji bonae jusigesseoyo) = would you send it by tomorrow?
Professional, to a client or a contact at another company.
The general rule
The bigger the favour and the higher the person, the further down the ladder you go: from command, to question about willingness, to question about ability, to wondering whether it might be possible. Each step adds distance, and in Korean, distance is respect.
One thing I am unsure about
Some guides say 주시겠어요 is becoming slightly stiff and that 주실 수 있을까요 is now the more natural soft request among younger professionals. That fits what I hear, but the two overlap so much that I would not tell a learner to avoid either one.