I usually use it in a stir fry or soup, but also do a side dish of stir fried veg, with any suitable ones I have, inc. shredded cabbage. Goes v well with egg fried rice, usually with a few bits of leftover chicken added here, or a few little prawns.
IIRC just a little oil, sauce made of 2 tbsps water, 2 of oyster sauce, 1 of soy ditto. I will usually add garlic, plus red chilli and ginger pastes, which more often than not come out of little jars from Asda.
We use Pak Choi as a veg side dish with anything. It looks very elegant cut in half vertically and steamed. I usually make a sauce to go with it with onions, colourful peppers and mushrooms with a little soy sauce. It works well with things like pork chops, roast chicken etc.