The way he…

smiles with his eyes and a wide-open mouth, sticking out his tongue (see above)
giggles when his dad or I kiss him repeatedly on the neck or tummy
snorts when he is about to cry
falls asleep while nursing
“phantom nurses” while asleep by working his little mouth every minute or so
stretches like a kitten after a nap or stint in the car seat
after crying, does a “sniff sniff, sigh”
sighs periodically in his sleep
sleeps with his arms outstretched to the side or extended up to his ears
“makes himself heavy” when he doesn’t want to be picked up
rests his hand on my boob while nursing
“talks” to my boob when I don’t get him on there fast enough
raises his legs up while staring at his cloth book
pulls off while nursing to look into my eyes for a few seconds, then pops back on
the way his eyes roll back in his head when he nurses

Added 4/16/05:
smiles so wide that he drools out of the corner of his mouth
the way his forehead crumples up when he cries
the way he doesn’t look at me when he is “mad”
laughs when I lift him up and down in the air really quickly

will add to this as I think of stuff!