If you've tried everything and the baby is still fussy its time for a nap. Wrap the baby up, and place it in the crib while still awake and let the baby fall asleep. Here's more about crying:
I think its important to make a distinction between abnormal and normal crying.
Abnormal crying times include: during feedings, immediately after feedings, and times when a baby wakes early out of a sound nap. Crying during these times requires attention, and child should not be allowed to "cry it out"
Normal crying times include: just before a feeding, when a baby is put down for a nap, and during the late afternoon/early evening period. The type of crying you are asking about is when going down for a nap. The duration of this type of crying is set by the child, but monitored by the parent. The American Academy of Pediatrics recognizes that: "Many babies cannot fall asleep without crying and will go to sleep more quickly if left to cry for a while. The crying shouldn't last long if the child is truly tired."
It is not unusual for a sleeping baby to occassionally begin whimpering or crying softly in the middle of a nap. Again, the words of the American Academy of Pediatrics are helpful in understanding what is going on. "Sometimes you may think your baby is waking up when she's actually going through a phase of very light slumber. She could be squirming, startling, fussing, or even crying--and still be asleep. Or she may be awake but on the verge of drifting off again if left alone. Don't make the mistake of trying to comfort her during these moments; you'll only awaken her further and delay her going back to sleep. Instead, if you let her fuss and even cry for a few minutes, she'll learn to get herself to sleep without relying on you." The Academy goes on to say that "some babies actually need to let off energy by crying in order to settle into sleep or rouse themselves out of it. As much as fifteen to twenty minutes of fussing won't do you child any harm. Just be sure she's not crying out of hunger or pain, or because her diaper is wet."
Identifying and knowing your baby's cry patterns and disposition (personal style) will hepl you learn to discern real needs.
This is for babies as young as a couple of weeks old