Like most of the lore surrounding misunderstood subjects, the popular ideas about smoke signals used by Native Americans are mostly inventions by the movie industry.  To put it in context, the signals were just that - signals.  It was not some Indian Morse code and did not have detailed information encrypted in smoke columns.  It was a pre-arranged signal used by one party to alert another party at some distance about some "yes" or "no" event and involved the interruption of the column using a robe or blanket in a pre-arranged method.  Sort of like the lantern on the Old North Church.  Sometimes it was just the column of smoke itself.  Simply said, the signal was a short message which would usually be vocalized by one or two words.  Uncomplicated but it worked!