Jews and Christians share a good portion of the Old Testament, the portion of the Bible which prophesies the coming Savior. Christians accept that Savior as Jesus and most Jews do not.

Within the Torah (the first five Books of the Bible), God gives the Jews various laws, which can be divided into Purity Law (cleansing yourself to go before God), Cultural Law (how the Jews should structure their society) and Moral Law.

Since morality is by nature timeless and perfect, it is what forms Judeo-Christian values, shared by both Christians and Jews (not that Jews can't also be Christian, as are Messianic Jews).

There are certainly arguments to be made about how well it has been applied, or how accurately, but those values shaped Western Society and the inspiration for Constitutional Rights. For how effective it's been, I think the proof is in the pudding.