How Christians decided what went in the Bible

What books were or weren't in the Bible wasn't agreed until 367CE. Up until then, some Gospels and letters were used that aren't now in the modern Bible. The Council of Laodicea met, with all the church leaders there, to decide what books were in and out of the Bible. Some books were excluded because they obviously taught teachings that weren't Christian. Others were harder to decide upon. For instance, some early Christians didn't want the letters of John in the Bible.