Luke 12

 We often hear the Savior's words- 

"...take ye no thought how or what thing ye shall answer, or what ye shall say:

12 For the Holy Ghost shall teach you in the same hour what ye ought to say."  (Luke 12:11–12)

But seldom hear the precursor - 

"...when they bring you unto the synagogues, and unto magistrates, and powers..."  (Luke 12:11)

Which suggests to me that this is immediate with no time for preparation.  When time restrictions are not limited, I believe the Lord wants us to ponder and pray in preparation and the Holy Ghost will inspire through that period.  

In my mind it doesn't mean that you should not prepare and just depend on inspiration.