Many religions are based on what you do or don't do. In order to be classified as "practicing" that religion you have to meet a list of qualifications. Do you do this and not that? Christianity is a little harder to define with all of its different denominations (some that require different things) and with a wide variety of people claiming to be Christian and not doing anything. What makes a "Practicing" Christian would then depend on who is answering the question, but if you are careful to identify the characteristics and the dos or do nots of the Christian faith then you would find your answer a little more simple then that.  

Christians believe that their religion has roots in the Jewish religion and even share some of the same Canonical texts. They believe that a Messiah or Christ was born of a virgin and through him (Jesus) they are redeemed from their sin. Because of this they no longer need the rituals of the Jewish religion and the sacrifices that were up to that point required.

Originally Christians were former Jews. However, the religion spread and took on new forms and shapes. Some groups continued to do a number of rituals that became an essential part of their beliefs. Others didn't do the same rituals or even believe that rituals were necessary. However, the varied beliefs took thousands of years to arrive at the vast amount of beliefs today.  

The term "Christian" means to be Christ-like. It should be the goal of Christians to be like Jesus (the man they believe is Christ. This would mean that the rituals of the past and those later created aren't necessary to be a Christian. Jesus told his followers: "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.' Matthew 22:37-39 NIV He also talked about following the ten commandments, "You know the commandments: 'Do not murder, do not commit adultery, do not steal, do not give false testimony, do not defraud, honor your father and mother.' Mark 10:19 NIV These are the things that Christians are supposed to do.  

Church is a fairly well established practice having been around for thousands of years. However, is it necessary to go to church in order to be a Christian?

The first Christians would meet in houses. Their purpose was to learn and to uplift each other. Being a Christian was hard and often came at a price. It was because of this that they wanted to lift each other up and encourage one another. This wasn't a "Sunday" or a "Saturday" event, but rather something they did when their lives would allow.

Church has become something completely different and is often very ritualistic. It is not a necessary part of life that Christians must participate in. In fact, many of those who go to church every Sunday aren't working toward following all of Jesus' commandments (after all few of us can really say that we love our neighbor as ourselves). Church is often seen as the requirement for a Christian, but in reality it is just a practice that has taken over and isn't required to be a Christian.  

Being a practicing Christian requires learning the history of Christianity. For a very firm grasp it is a good idea to learn the division of the various denominations and what they believe. However, the most important part of being a practicing Christian is to try and follow the teachings of Jesus the Christ. This doesn't necessarily mean that you have to go to church, but it does mean that you have to learn what the Bible says and how to put it into practice.