The most important is that there really is a God. That Jesus is alive and rose from the dead.
The next thing you need to realize is that saying you are Christian and being Christian are two completely different things.
To truly be Christian you must admit there is a God and that Jesus is His son. In addition, that Jesus did not sin and was placed upon the cross in your place for your sins. Your own sins that can be found and listed within the Bible, sins you will try not commit any longer for you will know they are wrong. When Jesus rose from the dead, He had just returned from hell where he took the keys of that place from Satan because humankind could once again stand clean before God through the bloodshed upon that cross.
When you truly come to understand the teaching of Christ, you will come to understand that being a Christian is something that is not easy to do.
You will strive not to use curse words, yet you will and it will leave you feeling shame afterwards. You will come to place all others before yourself, but many times, you will be selfish and self-serving. Then you will realize you have sinned once again.
Being truly Christian, you will become aware of this feeling of guilt more than any other emotion, because being Christian is not easy.
There are those that teach that within you is your salvation, but this is a lie. For all that is within you is you. You can feel the presence of the Holy Spirit for that is the part of the Holy Trinity that comes in physical contact with all that accept Christ as their savior. Inside you through your soul you will come to know that the thought that comes to you to help you did not come from inside you but from outside and above.
Is it an angel? Is it Jesus? Is it even God talking to you? We do not know at this time, but someday we will. It is important though to realize is that it is not inside us but above us and can work through us for we are the body of Christ upon this world.
In time, we will learn that material possession and money are of the world and so have no true meaning to those that call themselves Christian. They will be just something that is necessary to get by in this world, but you will not go out seeking more and more. For if you do you are seeking your reward here upon this earth, which is not promised to us. For our reward will come in the next life. It states in the Bible that if you are rich your reward well be less in the Next life, but if you are poor, greater will be your reward in the time to come.
This last sentence brings me to the most important part of being a Christian. Within the Bible, it teaches that all humanity is promised an immortal body, but it is to those that truly sought after being a child of God will the promised reward be given unto us. Jesus taught that greater would be our reward within this immortal and perfect body. God created an entire universe. It is there just too look at from this planet called Earth? I do not believe so. I believe the entire universe will be opened onto to those that accept that there is a God and accept that Jesus Christ is the Messiah.
This life is meant to be hard and harsh for those that say God is real. For if we endure and keep to that believe then we will be given this ultimate reward, which is to explore all that was created by God.