Summarize this article in one sentence.
Many babies get upset when they are in need of a diaper change. The feeling of the dirty or wet diaper against their skin is uncomfortable. Waiting too long to change a baby’s diaper can lead to diaper rash, which is very uncomfortable.  If you are using disposable diapers, the diaper will begin to sag or appear full. If you are using cloth diapers, feel the outside of the diaper to discern if the diaper is full. Some disposable diapers, like Pampers Swaddlers, have an indication strip that turns blue when the diaper is wet. Check for leaking near the legs or above the top of the diaper. Peek inside the back of the diaper to check for a bowel movement. A baby’s nutritional needs change several times in the first two years of their life. Signs you should watch out for in a newborn include smacking their lips, rooting, or sucking on their fists. You can tell if your newborn baby has had enough to eat by their fists. If a newborn’s fists are closed and near their face, they have not had enough to eat. If their fists are open and relaxed, they are satisfied. An older baby may try to get into a feeding position or yank on your clothes if you breastfeed. They may become fussy, hit you, or turn their head from side to side. Babies, at any age, become fussy and cranky when they are tired. If they become too tired, they are inconsolable and difficult to put to sleep. You can also look for signs of sleepiness like yawning or eye rubbing. You should always be aware of signs that your baby is sick and not just fussy. If your baby shows signs of illness, you may need to seek medical attention.  Take your baby to the doctor if they have a fever over 100.4°F (38°C) and they are under 3 months or 102°F(38.9°C) if they are between 3 months and 3 years old. Seek help if your baby will not eat or drink. Look for signs of dehydration like less than 6 diapers per day or crying without producing tears. Make your baby an appointment if they have a cough that lasts more than a couple of days. Seek help immediately if your baby is having trouble breathing. Pulling on ears or a hoarse cry could be signs of a bacterial infection that may need treated with antibiotics. Trust your instincts. If you think something is wrong with your baby it is best to take them to a doctor. The doctor can make sure that there are no underlying issues that are causing your baby's discomfort. Although it's likely that your baby is just experiencing normal crying, it's best to err on the side of caution.

Summary:
Determine if the baby needs a diaper change. Decide if your baby is hungry. Discern if your baby is tired. Check for signs of illness. Visit your doctor if you can't identify a reason for the crying.