Taxis and directions: "Wo yao qu..." (I want to go to...), "Duoshao qian?" (How much?). Show the driver the Chinese address or a map on your phone — safest of all.
Eating: "Zhe ge" (this one) while pointing at the menu, "Bu yao la" (no spicy), "Mai dan" (check, please). Photographing the dish and showing it to the staff works better than a hundred sentences.
Help: "Qing wen..." (Excuse me...), "Cesuo zai nali?" (Where is the toilet?), "Jiu ming!" (Help!). Download translation apps (Baidu Translate, Youdao) with offline packs.
