Captain and stoker are what the two riders of a tandem are called. The captain at the front bears the responsibility for the ride à deux. That is quite simply the nature of the beast as ultimately he can see where you are riding to. And as communication is known to be good for any relationship, he must in his role as chauffeur make his rear man, the stoker, aware of oncoming traffic or bends in good time. The back bencher simply does not see much from the 2nd row. But this describes the attraction of this unique form of mobility: the trust-based interaction of a well-practised tandem crew on said bike.
One bears the responsibility – the other pedals along, as you both pedal in unison and stop together. When starting to freewheel, the pedalling action should not just be stopped suddenly, but you should soft pedal without pressure until the rear man understands the signal and stops applying pressure to his pedals. In contrast, the rear man must not want to steer, he must trust his captain and should also not stop pedalling abruptly either.
It is advisable to take the tandem out for test rides on roads with little traffic, where you don’t have to brake too much, stop frequently or turn corners. It simply takes some time until two independent cyclists become accustomed to the unfamiliar new roles.
In practice, the captain mounts the bike first, holding it in place on the top tube with his thighs if necessary. The stoker then takes his place on the saddle and places his feet on his pedals. And when having to stop en route, the rear man remains seated, the front man will hold the bike upright. This should also work out with some practice, if the captain is slightly lighter than the stoker. But do be aware: If the rear man is considerably heavier, the tandem can no longer be steered. Therefore, the rule for assigning the seats on a tandem is always the same: the larger rider at the front and the smaller, lighter on at the rear.