My edited answer from another similar question.
First, it is very likely normal for your baby to cry and you need to ration your strength. Make sure both parents and other caregivers give each other breaks from the crying to recover. If it is just the two of you please find some help. Even as little as a couple hours once a week is important for your health and ability to have perspective.
Now, strategies for crying. Go through a cry reasons checklist in your head every time until your reaction is automatic, here are mine:
- Wet (change diaper)
- Hungry (feed)
- Gas (Burp)
- Cold/Hot (adjust amount of bed clothes)
- Uncomfortable (check the baby's body for anything that could be an irritant: don't overlook things like clothing tags, detergent used, a hair wrapped around a baby's toe, perfume on a parent)
- Tired (soothe and later ignore)
- Upset/Angry (try to remedy the upsetting environment, soothe, or ignore)
If the baby is still crying you need to look outside healthy, normal reasons for crying. Start checking for such things as:
- Rash
- Fever
- Alergies (what is mom eating that could be an alergy?)
- Infection
Once you have a checklist in mind you need to keep track of a crazy amount of stuff: what is the baby eating, when, when is the baby sleeping, how long, any burps, how about diaper changes, and so on. If you have these things in mind you can start to identify what leads to crying in your baby. Keep it all in a little notebook and bring it with you to doctor visits just in case to help remind you of things. If your baby continues to cry call your doctor or nurse helpline. You may need to go in for a visit.