Each of the links below is to a YouTube video:

What is Apologetics? (Youtube video)

Learn How To Do Apologetics in the Twenty-First Century with Ravi Zacharias (1 Hour)

Ravi Zacharias International Ministries YouTube Channel

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Here are some basic apologetic questions answered on YouTube about different world religions popular in America today.

Mormonism:

Do Mormons Believe In The Same Jesus As Christians?

Islam:

What is Sharia Law?

What is Jihad?

Does The Quran Have Any Historical Veracity?

Is Islam A Religion Of Peace?

Secular Atheism:

Understanding New Atheism

Jehovah’s Witnesses:

Who Is Jesus According to Jehovah’s Witnesses?

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Here are some good books on apologetics (with amazon.com links):

Tactics by Gregory Koukl

Evidence That Demands a Verdict by Josh McDowell