Fluency is directly linked to comprehension.  Student fluency is a good indication of their comprehension or understanding of the text they are reading.  Fluent reading (smooth, at a nice pace with lots of intonation and attention to punctuation ) indicates that the student is making sense of the text as they are reading.   Poor fluency often means that a text is too difficult.  Students working in a text too difficult will lose meaning while working on decoding the words they are reading-more effort being used to solve words affecting how well the student can read for meaning.

This sight has some nice activities to promote fluency with your classes
 

http://www.teacher2teacherhelp.com/reading-strategies/fluency/promoting-fluency/

Printable Scripts for Reader's Theatre

http://aaronshep.com/rt/