Are there any specific rules on everyday life at all in Christianity? Christianity seems to be one big category with a long list of denominations. To my knowledge, there is no "Christian language" in the same way as in Islam (Arabic) or Judaism (Hebrew) or Hinduism (Sanskrit). I have noticed that some Christians do recite verses from the Bible, but they do so in the vernacular language rather than some obscure or archaic liturgical language that is typically the language of the scriptures. For Christianity, I would probably expect that Christians would recite the verses in koine Greek and biblical Aramaic. Nope, more often than not, they recite in the vernacular. Are there any specific rules at all in any denomination of Christianity?


Rules about prayer, meditation, and devotion (when to pray, how to pray, how many times to pray per day, where to pray, in which direction to pray)
Rules about diet and fasting (when to eat, how to eat, how many times to eat, where to eat, what to eat and what not to eat)
Rules about pilgrimages (which sites are holy, how to behave on the holy site, whom to meet on the holy site, what to expect on the holy site, how to pay respects on the holy site)
As broad as it may appear, here is how we can summarize it.


  Matthew 22:35-40 (NIV) 
  
  One of them, an expert in the law, tested him
  with this question: “Teacher, which is the greatest commandment in the
  Law?” Jesus replied: “‘Love the Lord your God with all your heart and
  with all your soul and with all your mind.’ This is the first and
  greatest commandment. And the second is like it: ‘Love your
  neighbor as yourself.’ All the Law and the Prophets hang on these two
  commandments.”


Christians should live their every day life by following two simple commandments,


Love your God with all your soul and with all your mind
Love others as yourself


Our customs/rituals on how we show our love to God may vary but they all fall under the same command. Christians should practically demonstrate God's love to others.