My grandma, who was a pediatric RN, scolded me one day when my oldest child was just a couple of weeks old. He was very fussy and rarely settled, even after a nursing. "You need to wrap him! Snug!" She explained that babies, especially large babies, love to be swaddled. "They feel at home that way, just like in the womb. Otherwise, they will feel insecure and bonk themselves in the head with their own arms." I had noticed him hitting himself, often waking himself from sleep.
She then proceeded to show me how to swaddle a baby. Grandma had no use for the modern day receiving blankets. "Too small!", she exclaimed. She found some soft flannel and made a couple of large blankets for me to use for my big baby. "Swaddle him for the first nine months and you will have a happy baby.", she said. "But what about learning to crawl?", I asked her. "When he wants to crawl or be removed from the swaddling blanket, he will let you know."
I took Grandma's advice to heart and my baby became much less fussy by the next day. After that, I swaddled him regularly to combat the overstimulation that he often expressed.
Grandma was also a big fan of what she called "fanny pats". :) She would put the swaddled baby on her shoulder and pat his bottom gently like a cadence. Usually this brought forth any excess gas in the form of a burp and the rhythm helped the little one to sleep.
Here is our own little Annie swaddled in a toasty blanket.

Aussie Annie, has posted a wonderful tutorial on how to swaddle your baby. It takes some practice but is a great way to keep a calm baby happy and help an unhappy baby to settle in.