The premise of most Christians (at least rational ones) is
1. God is the creator of the everything including humans.
2. Being His creation God knows the best way for us to live our lives as documented throughout the Bible.
3. Being made in God's image we are bestowed with free will which includes the choice to sin (live according to our own will instead of God's).
4. We will be judged for said decisions and punished/rewarded accordingly.
5. Everyone sins, since were all human with basal desires.
6. We can find salvation through Christ.