First they strap the baby to a special device to stop it from moving. At this point it will probably be crying due to fear caused by being separated from it's parents. Next they may or may not anesthetize the baby. If they do there is a very real risk of death, and since it does not completely eliminate the pain, many choose not to. Next the foreskin is removed. At this point the baby may go into shock and become quiet from the intense pain associated with cutting one of the most sensitive parts of their body, coupled with a newborn baby's greatly heightened pain sensitivity.
Then the wound must be carefully cleaned to prevent infections, or adhesion - both of which may require further surgery to fix. After which your child will have to live with increased risk of infection, decreased sensitivity, increased risk of contracting AIDS and other STIs, along with a host of other complications. Furthermore, there is absolutely no reason for it to be done at birth. The chances that your child would need to be circumcised for a medical reason are tiny, and the circumcision can be performed at the time it is required, if ever.
Here is some further information.
Please don't do it.