We use around 50 codes and words or a combination of coedes and words(eg bump one).(so many because offroad tandeming is more complex). Numbers are easier than words when there is a lot of wind.
We also have different mother tongues. So we use numbers in English. Numbers are also faster to say.
U have to find out what works for u both best while riding. We started with ten. But ther are so many kinds of bumps and traffic situations.
75% codes comes from me 25% from her. (stoker even when not blind does not see very much of what's coming) In the beginning this is far too complicated. Then it was : do like me.
Stand up for every bump is the fastest signal in the beginning.
Number one :
Clicked in?(stoker not me) My position is like the one described by Leisesturm.
Very important :say when u're going to brake and how hard: the stoker can get thrown of the saddle. I lost pedal contact is also a very important message.
Since DI2 and only one chainwheel, warning for shifting less important.
It's important to tell if one of u is going to move on the bike or let go of the handlebar. (drink, food, turn around, take photo etc).
Certainly when the frame is not so stiff and the stoker is not a lightweight.
Very important is : finding a way of riding both standing on the pedals, to relief pressure when climbing.
On the flat u can standup without pedaling, uphill this does not work.
When i cycle alone i move the bike from the left to the rigt, with her we move our bodies, not the bike.
New thing she had to learn : time the pedals. Other tandem pedals were always timed.
If stoker wants to stop pedaling also important. On the new bike I can stop pedaling ans she can go on.
And don't forget the stoker is allways right. The captain has to make the stoker happy. No tandeming possible without a stoker.
So make compliments, talk about imrovements, say sorry when u make mistake or something goes wrong.Say thank u for the nice ride.