It's a common occurrence in an evangelistic lifestyle. You're talking to someone about Christ only to find that the person you're talking to believes in the doctrines of some other religion.
Hinduism, Mormonism, New Age, Unity--the choices are endless. So how do you find out what he or she believes and how to use those beliefs as a bridge to Christ?
It's important for any on mission Christian to learn how to interact with people of other belief systems and understand what other religions believe. The classic reference book Handbook of Today's Religions is still one of the finest resources available to help you meet that goal.
The short chapters are easy-to-read and concise but filled with vital information about the history and the doctrines of other religions and other helpful information, such as terms and key leaders.
Before getting into other beliefs, however, McDowell and Stewart first present evangelical Christian doctrine to establish a plumb line for measuring and investigating the belief systems of other religions.
The book even closes with a walk through the "Four Spiritual Laws" to help acquaint readers with a ready-made, easy-to-follow presentation of the gospel for when they encounter those of other faiths.
The Handbook of Today's Religions covers the wide variety of religions that exist, from the known (Hinduism, Buddhism, Mormonism, etc.) to the little-known (such as Rosicrucianism). Keeping a copy on hand can be a great way to remain informed about the multitude of beliefs around you.
That way, you can be ready when your personal evangelism efforts take you into a world that's filled with so many errant beliefs--beliefs that are keeping people from coming to Christ.