Taxing an aircraft is easy. Knowing where to go is the difficult part. What must be understood is that taxing an aircraft is a two man job, it makes no difference who is taxing the aircraft at all. Your primary role as PNF/PM on the ground is to monitor the track of the aircraft, as it is in the air. As PM you should be telling the PF when to turn and what holding points should we expecting to see. With PF looking at his chart as well this is a good error check. Having your head down doing control checks or before take off checks while letting the PF blindly taxi on his own, before establishing that both of you are happy with the intended route, would seem to me to be poor airmanship.