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 :)