This may be somewhat controversial but I believe a baby has different cries for each of its needs. That's not to say I learned each and every cry but I definitely followed other cues to determine what my babies needed at any given time.
Here are a few things I wished I had known with my first child so I could have done things differently with each of my other children:
Did you know a baby usually squirms and wiggles to cue its need to pee? I learned this in my study of potty training in other cultures. If the cue goes by unnoticed, then the baby will pee and either get fussy or cry. If the cry goes unnoticed, the baby learns to sit in its pee. Interesting, eh?
Babies also have a cue for bowel movements. The obvious newborn explosions and grunting but also passing gas and body language can announce their need to go number two.
Babies also cry if they are bored, overtired, anxious or suffering from tummy pain or plain just need comforting.
I never had a baby with colic and with most of my babies I tried to attend to their needs the best I could when they cried. But there were times with my first babies I had no clue as to why they were crying. We resorted to baby carrier next to the washer and dryer, a drive or walking around. With the others, to be honest I would nurse them. The majority of the time they would accept the offer and settle down and go to sleep at my breast.
I have researched the Dunstan Baby Language and find it SO interesting - makes sense to me :) Are you familiar with this Theresa? I am trying to STUDY before someone makes their debut hehe