Christianity started off as nothing more than a sect of Judaism, so many of the Jewish teachings also apply to Christianity, for example the ten commandments.
However, since those who spread Christianity wanted lots of people to convert really quickly, they abolished some of the more outdated or strict rules (such as dietary restrictions), and obviously the peaceful teachings of Jesus emphasised.
But apart from that, most of the laws and teachings are very similar.
The Torah only requires Jews to follow the law of the Torah. According to Judaism non-Jews are obligated to follow just the 7 Noachide laws which are described at http://www.answers.com/topic/seven-laws-of-noah
Orthodox Jews follow nearly all the laws. Conservative follow some, but not all. Reform Jews follow little or none of the laws.
It gives them laws to live by.
Jews first and foremost follow the laws of the land.
Christianity does not require the observance of the sabbath law. Christians are not party to the old covenant that requires sabbath observance.
By learning it and observing its laws.
They follow some of the muslim principles not all the principles , examples of these principles laws of marriage, divorce, inheritance, etc. In the meantime, other religion followers (Christians and Jews are allowed to apply their own religion rules and laws related to these issues.
There's no exact number, but it's mostly Orthodox Jews who follow the dietary laws.
Peter
Read the Holy Bible and pray to God.
The Jews follow many laws. Most of them are written in their Bible, called the Torah. The most important laws are in the Ten Commandments, which the Jews believe were written by God. the Ten Commandments are the basic structures of Judaism. For more information, see the attached Related Link.
The kosher dietary laws were designed to preserve health standards, and it's mostly Orthodox Jews that follow these laws.