Birth

If the new baby is a boy, he will be named at the brit mila (circumcision) on the eigth day or as soon after that as possible. Jewish law only considers a child viable afther his eigth day. If she's a girl, she will be named during a synagogue service in a ceremony connecte to the reading of the Torah. This is usually done on the first Shabat after she's born. A special 'mi sheberach' is said, usually by the father: this starts with a prayer for the well-being of the mother and is followed by the naming, usually followed by a prayer that this new Jewish daughter may grow up a good, wise woman.
In both cases, of course, this has to be celebrated with food and presents!