I'll add on to the "comfort crying baby" point ... once you cover the basics (clean? fed? dry? warm? burped? etc), sometimes babies just cry, and that's ok. Obviously you should be mindful and watchful over their condition, but there's no need to be stressed over a crying child in the short term as long as you've made sure everything is ok.

I'm only mentioning it because with my first (daughter) I would get really stressed and worried if she continued to cry after I did all the above. Just talk to them, play with them, and all will be good :)