Many theologians are concerned with the question of what it means to live a Christian life in the modern world. The best-selling book, In His Steps by Charles Monroe Sheldon, for example, recommends that before doing any action, one should ask "What Would Jesus Do?"
The theological issues involved are fairly complex. The first major controversy among Christian theologians has to do with the Mosaic laws, i.e. whether the Christian is obligated to follow all, some, or none of the Old Testament precepts set out in Leviticus. While very few Chjristians now follow the ritual laws of the Old Testament (avoiding shellfish, menstruating women not being allowed in church, etc.) there is a question about whether laws respecting the Sabbath and marriage and moral laws were replaced or sustained under the New Covenant (thus the debate over gay marriage, controversies over contraception). Jesus seems to imply in some places that his followers do not need to follow Levitical laws but in other places that they should follow them.
Two other issues being debated are whether "stewardship" over the land means living in an environmentally responsible fashion and what obligations are entailed by Christian charity.