Hi Jerry, for any Chinatown in the world, always look for the ones with lots of Chinese people eating in them. Sounds simple but if you walk around Chinatown in London, only 4 or 5 restaurants will have a significant number of Chinese families eating in them. Those are the ones to go for!
As for generally speaking, I usually pull up a Google map of the area I'm going to then type in restaurants, or indian, or chinese e.t.c. in the search bar and it will bring up all the local matches most of which have reviews collated from other sites. There is still no guarantee they are genuine reviews but it will give you a good starting point.