Below is a video of An Introduction to Contemplative Prayer by Jim Williams at Church of the Redeemer. The overview that Jim gives assumes a Christian context and that his listeners are committed Christians. Christian Contemplative Prayer occurs in the presence of God by people who are filled with the Holy Spirit. Without the relationship to the Father, Son and Holy Spirit, the act of engaging in contemplation can open a person up to negative spiritual experiences. Christian contemplation is a spiritual discipline that is done by a Christian who lives an active devotional life in a Christian community. Links to the books Jim references are below the video.
Open Mind, Open Heart by Fr. Thomas Keating
The Practice of the Love of Jesus by Alphonsus Ligouri
The Cloud of Unknowing & The Privy Counsel by An Anonymous Author
Church of the Redeemer 