Spitting:

One thing that surprises most visitors to China is the common habit of spitting. This can happen pretty much anywhere outdoors. However, local governments are stamping out this practice across the country, especially as China becomes increasingly conscious about their world image, partly as a sign of changing times and partly because of the Olympic spotlight. Refrain from copying the locals and spitting, as they will curiously watch every movement a foreigner makes. It may sound rather hypocritical but there is a conception that foreigners don’t generally do that sort of thing. Don’t be too disturbed if the old man who grins inanely at you and gives a friendly wave of pleasantness suddenly fires out a mammoth clob of phlegm onto the pavement. They are often aware of the vulgarity of spitting in public and perhaps because of this concerted efforts are being made to stamp out this unhygienic practice.