At this perpetually packed local institution, the seafood is crawling/swimming/blinking at one end of the room where you put in your order. Everything is priced, even the veggies; you just point at what you want, and they'll go off and cook it.
There are various cooking methods – sautéed without chilli (清炒; qīng chǎo), fried with chillies (辣炒; làchǎo), cooked with with ginger scallion (姜葱; jiāngcōng), slow braised (红烧; hóngshāo) – but it's tough to convey exactly what you want without being able to speak Chinese, so just go with the flow; it'll be delicious.