The letters bet, vav, mem, and pay all come from the lips.
The letters dalet, tet, lamed, nun, and chet come from the roof of the mouth.
The letters zayin, samech, shin, reish, and tzadi come from the teeth.
The letters gimel, yud, kaf, and kuf come from 'Hachecha' (lit. smile) - I think this means a facial expression of slightly open mouth and tongue on the bottom of the mouth
The letters aleph, chet, hay, and ayin come from the throat.
One is supposed to be mesameach the chattan v'kallah by telling them how great they look etc. otherwise, they are losing out on the five kollot, i.e. all the letters of the aleph-bet.
I thought it was interesting