During the first month, baby should have about 1 substantial bowel movement a day. After this first month, though, the pattern can change. Breastfed babies who are older than 1 month can go as long as two weeks without a bowel movement and be perfectly normal, as long as it is normal when it does come. By contrast, they can also go every day and also be normal. When in doubt, always call a doctor, but generally, if the stool is loose and mustard-y, there isn't anything to worry about.
Wet diapers are another indication of baby's intake.
Around the 4th day of life, your baby should have 6 soaking wet diapers in a 24-hour period. If, after the 4th day, you see any pink or red in the urine, that would be cause to think that baby wasn't getting enough to drink. Also watch the baby while you are nursing. Pay attention to the way that he suckles at the breast. You can also occasionally hear swallowing, which is nice, but some babies swallow so quietly that you can't hear them.