Only if your partner requests it,
or places you in an unsafe position
(such as squeezing hands too tight)
one should not provide dance advice
outside of a classroom setting
or dance practice session.
Otherwise, "teaching" may place
your partner in an awkward place
taking the fun away from the
social dance experience.
I personally do not go into
teaching mode unless someone
knows I am a dance teacher
and asks me for advice which
I gladly have provided :)