I have tried a search for guidance on tipping drivers and English speaking guides hired for private transfers in Beijing, but no luck on this particular question. We will be using a private transfer from PEK to our hotel provided by the Grand Hyatt Beijing at a cost of about $110. Then we will be using a private transfer with another couple from the Grand Hyatt to the cruise ship terminal in Tianjin which will cost $275 for a driver plus an English speaking guide (although there will be no tour- the guide is just there to provide necessary information in English).

Is it customary for Americans to tip each of these services and, if so, how much? Separate tips for the driver and the "guide" ?