What do we do with his towel? (guest side)

We don't share it
We do not tie it around the neck (unless we are a child or very old)
We don't fully unfold it
We never blow our noses in it or sponge up any catastrophe
You don't dip it in your glass
You don't spin it frantically above your head...

But then, how do we do it?

We wait for the hosts to give the 'La' to place her on her knees, slightly unfolded.
If you have to leave the table, place it delicately crumpled on the right side of the plate.
And if a stain appears, we are responsible for trying to hide it with an opportune folding.