The consumption of alcohol and swine is forbidden; they all believe in the same one god; they all believe in prophets; the afterlife; the holy land of Jerusalem is sacred to all; all pray and have certain holy days of the week (Friday for Muslims, Saturday for Jews, Sunday for Christians); all believe in some level of modesty (like the head cover for Muslim women, Orthodox Jewish women and Nuns); all have really similar holy books (Quran, Bible, Torah); all do some sort of fasting (Muslims for Ramadan and Yom Kippur for Jews. Some Muslims also observe Yom Kippur).
Good luck.
