Guile is defined as craft, cunning, duplicity, and deceit.  It is found in the man and is manifested by what he says.

Ps 32:2 Blessed is the man unto whom the Lord imputeth not iniquity, and in whose spirit there is no guile.  So, it is in you, in your spirit, first.  Notice Jn 1:47 Nathanael… in whom is no guile.

1 Pet 2:22, Rev 14:5 It’s also in your mouth. It manifests itself in what you say.  1 Pet 3:10 The ones, in whom there is no guile, speak no guile.

Those with guile in them:

Lie.  But they are so crafty they make it look like they’re telling the truth.  Notice the accusations against Jesus in Lk 23:2, or Paul in Acts 24:1-7.  These words are so carefully crafted they sound like the truth.  However, they are absolutely false.

Tell some truth.  But they don’t tell all the the truth to deceive you.  They leave out important true details that totally change the meaning of what they are conveying to you.  Contrast Nicodemus’s words in Jn 3:2 with the words of the spies from the chief priests and scribes in Lk 20:19-21.  These are basically saying the same thing.  However, Nicodemus spoke without guile, while the spies spoke with it; they were lying.  

Craft their words.  They do this to cleverly disguise their true intentions.  In 1 Thes 2:1-6 Paul assured the Thessalonians that he was not using guile when he preached to them.  He may have been tempted to avoid the contention or to please men or to seek glory.  But he didn’t do this as the men who had visited the Thessalonians had done.

Conclusion: Now that you see what guile is and where it comes from, don’t do this.  If you see that you have it in you, deal with it on the inside so that you won’t speak this way any longer.