Avoid false prophets

Matthew 7:15  "Beware of false prophets, who come to you in sheep's clothing but inwardly are ravenous wolves.

Matthew 24:24  For false christs and false prophets will arise and perform great signs and wonders, so as to lead astray, if possible, even the elect. 
1John 4:1   Beloved, do not believe every spirit, but test the spirits to see whether they are from God, for many false prophets have gone out into the world.   See also: http://www.gotquestions.org/false-teachers.html