There are large numbers of mutually exclusive religions in the world that claim to be Christian, as well as heretical views that are compatible with those false denominations. The thing about the Christian faith, however, is that we actually have a Holy book. An instruction manual, if you like. Or one could call it God's autobiography. Some have even constructed the following acrostic. The Bible is:
Basic
Instructions
Before
Leaving
Earth.
Unfortunately, each false view has a defence against the Bible: Simply claim it's open for interpretation. It says one thing, but really it means something entirely different.
Take, for example, Theistic Evolution. The Bible repeatedly affirms that God made the heavens and the earth in 6 days. Exodus 20:11 even goes as far as to say, verbatim, that "in six days the Lord made the heavens and the earth, the sea, and all that is in them, and rested the seventh day." This is not a difficult concept. But many people out there want to say that when God said 6 days, what He really meant was some extremely ambiguous periods of time, during which He did basically what the atheists claim happened.
Then there's the Catholic Church. Sola Scriptura is a demonstrable Biblical doctrine, particularly with 2 Timothy 3:16-17, but to a Catholic, when God said "All Scripture is given by inspiration of God (...) that the man of God may be complete, thoroughly equipped for every good work", what He really meant was that scripture is subject to the authority of the Church, and that there's a lot of doctrine that you can only get from the Church.
Mormons do it too. The Bible says Mary was a virgin, Mormons say Jesus was conceived when the Father literally had sex with Mary. So, what God really meant by Mary was a virgin was apparently Mary was not a virgin.
If you believe in an omniscient God, you must necessarily believe He is not such a terrible communicator as to say one thing but mean the exact opposite. He knew what He wanted to get across, and He did it. With the Bible, the correct interpretation of the text comes from just reading it.
The most important thing the text says is that all have sinned, that the wages of sin is death, but that God so loved the world that He gave His only Son so that whosoever believes in Him would not die but have eternal life. If you confess with your mouth that Jesus is Lord and believe in your heart that God raised Him from the dead, you will be saved.