Renoncer
If you want a good brief summary of the false teachings of the Mormons and Jehovah's Witnesses, listen to the following two videos, from CARM (Christian Apologetics and Research Ministry):
http://www.youtube.com/watch?v=0b0UQaBJQRg
http://www.youtube.com/watch?v=Er-kXCIaCEE
If anyone is being deceived by either cults, make sure they know the truth about these false teachers in contrast to the truth of the Christian faith, for the salvation of their souls.
In Christ,
Renoncer