While having brunch at Sing Heung Yuen, a famous dai pai dong (street restaurant) in Hong Kong—known for its tomato-based soup noodles or macaroni, and crispy buttered buns—a non-Cantonese friend asked, “Does 寫嘢 (pronounced as seh yeh) mean menu?”
寫嘢 literally means ‘write stuff’, but it is a colloquial term used when you are asking the waiter to write down your order.
You can either say 寫嘢，唔該 (seh yeh, mm goi), or the other way round 唔該，寫嘢 (mm goi, seh yeh).
Since we are on this topic, here is an example of how a conversation in a restaurant (typically cha chaan teng or dai pai dong) would sound like.
Ching: 唔該，寫嘢。
Mm goi, seh yeh.
(I would like to place my order, thank you.)
Staff: 係，黎緊。要乜呀，小姐？
Haai, lai gan. Yiu meh ah, siu jeh?
(Okay, coming. What do you want, Miss?)
Ching: 我要個燉蛋，唔該 。
Ngoh yiu gor dun daan, mm goi.
(I want steamed milk pudding, thanks.)
Staff: 燉蛋。仲有無其他？
Dun daan. Zhong yau mou kei ta?
(Steamed milk pudding. Anything else?)
Ching: 係咁多， 唔該。
Haai gam dor, mm goi.
(That’s all, thanks.)
And when you are done with your meal, you typically bring the receipt that should already be on your table to the counter and 埋單 (maai daan, or pay for your bill).