What is the Christian (or your) perspective on Biblical apocrypha?

Many people take for granted that groups of people had to decide what was to be included in the Bible (I’m referring mainly to the NT here). In the 4th century, there was much debate about what books were to be included and eventually the New Testament as we know it came about. Different groups, however, include and exclude different books.

There were many books that were discarded and regarded as heresy, many of which present a very different picture of Jesus. The Gospel of Peter, for example, suggests Jesus was not human, but purely divine. The Gospel of Mary Magdalene suggests a more elevated position for women. The Gospel of Philip suggests that Jesus and Mary Magdalene had a special relationship.

My question is simply how do people regard these texts? How can we simply throw them out? How do we know which books are valid? How does the knowledge of apocryphal books effect belief?