Val writes,

<< what lip gets tickled by the nipple??
 This may seem funny to some, but some books say lower, some say
 upper. >>

Since the lower jaw is the one that moves, tickle only the lower lip -- and
gently.  If necessary, you can have the mom gently tickle the lower lip and
then very gently draw the nipple down towards the chin.  If you tickle the
upper lip, or try to go from the nose down to the chin, I've found a lot of
babies get confused and aren't sure what they are supposed to do.

Jan