Of all of the commandments in Judaism, the brit milah (literally, Covenant of Circumcision) is probably the one most universally observed. Even the most secular of Jews, who observe no other part of Judaism, almost always observe these laws.
Circumcision is performed on the eighth day of the child's life, during the day. As with almost any commandment, circumcision can be postponed for health reasons. The circumcision is performed by a mohel , a pious, observant Jew educated in the relevant Jewish law and in surgical techniques. Circumcision performed by a regular non-Jewish physician does not qualify as a valid brit milah, regardless of whether a rabbi says a blessing over it, because the removal of the foreskin is itself a religious ritual that must be performed by someone religiously qualified.