In Chinatown, Manhattan, Kam Chueh on Bowery just south of Canal, next to the parking garage. They are open late and are very accomodating to non-Chinese. The best way to order is to scan the menu and then ask the server what they suggest in each category - seafood, chicken, etc. Always ask what is the best (i.e, freshest) vegetable today. The waiters are friendly and good English-speakers. They will provide balance to the meal when they help you select.
They also have on a small menu, interesting casseroles. My daughter loves the goose intestines.
Another favorite is the t-bone steak with flowering chives.
Also on Bowery, north of Canal is Congee (NOT to be confused with Congee Village, further north on Bowery). Congee has a very extensive menu and very, very helpful staff.
Another major benefit to these places is that they both welcome BYOB, even though they sell wine and beer. We usually bring red wine and buy the beer from the restaurant. In the past, we've brought multiple liquors and mixers.
HOWEVER, the best quality Cantonese food may be in Queens. The best may be Gala Manor. It is designed for banquets, but has table service. It has an incredibly extensive menu with pictures and explanations. No BYOB here. Tuxed up waiters pour your beer and liquor is served from a rolling cart. Very high-end, but great quality and the one place I would take friends from HK or the Mainland.
Also, good for real HK style is Gourmand.
On Main Street, special notice should go to Little Lamb Family. This may or may not be a branch of a popular Northern Chinese chain that has reached all corners of China. It is a hot-pot/shabu-shabu restaurant where you get a basic broth set up and then order individual cuts of meat and vegetables to cook at the table. They are famous for their wide variety of organ meats, including penis, testicles, eyes, brain, etc. I suggest getting the lamb set 'yin-yang' - half straight lamb broth, half spicy and then going to town on the additional meats and vegetables. They have an interesting short list of unfamiliar Chinese beers. You can probably BYOB.
Happy eating!!!