As taken from the book 'The Happiest Baby on the Block', by Harvey Karp (a paediatrician).
My HV highly reccommended this book and its 5 S's technique to calm a howling baby. Based on the 4th Trimester theory, this only works for babies less than 3 months old.
I tried it for the first time yesterday and the results are unbelievable - I can't recommend it highly enough!
The 5 S's:
Swaddling - really tightly for it to work, with baby's arms straight inside the swaddle.
SSSSSSh - as loud as the baby's cry or other white noise (you may have to expt.). You MUST match the volume of the baby's cry for it to work.
Side - babies freak out when you lie them on their back when they're upset as they feel like they're falling. Lie baby on his side or on his stomach.
Swing (or shoogle) - match the vigour of uterine movements by swinging/jiggling really quite fast. If you think it's uncomfortable then it's probably just right for the baby.
FINALLY, when the baby is calm - Sucking. Feeding, thumb or dummy.
Once the baby is calm, he may start up again in 5-10 mins. Just start at the beginning again.......