Question: I own a 3 yr. old gaited Mountain Pleasure Horse. She is in the process of being trained by a professional trainer who trains  Quarter Horses. She said that she would have an open mind and help me start my horse gaiting. Now she feels this is not natural for a horse and suggest that I ride her like a Quarter Horse and not "ruin a good horse". How do I explain to her that this is natural for this breed of horse and I want her to gait? They have taught my filly to trot and canter. How do I correct this and start her gaiting? I have no one in my area who is familiar with these horses to help me.
 

Your trainer probably has no idea how to train your horse to gait.  I would 
advise you to take your horse out of there and work with the filly yourself.  
You can probably get the job done yourself.  Work only at the walk and the 
canter.  No reason to lose the canter.  

Use the flat walk and extended walk as the basis for your gait training.  I describe the "extended walk" as a "tiger walk".  It is a good, strong walk.  Do a lot of that.  Do not let her trot.  Over a period of time, ask for a little more.  If she breaks into a  trot, bring her back to her flat walk or ext. walk, then ask again.  Be patient and give her time.  At her ext. walk (and also flat walk), she will be working on a light, stretched rein.  Not collected.  Only when she can do these walks easily, without trotting, and on a stretched rein (with light contact), should you begin to ask for a little more.  Maintain the light rein 
contact - very steady and light.  To ask for more, use both legs evenly.  ( A light, steady squeeze with both legs).  When she starts to gait, even just slightly, maintain the light rein contact, but don't keep squeezing with your legs.  

Only do that when you want more impulsion or energy or speed.  You  will work the reins with very light, sensitive hands - using your fingers  more than your hands.  Do not hold the reins with a "fist", but lightly, with  your fingers.  When she does offer you the beginning of a gait, just go a few yards and then stop and pet her.  Always be very generous with reward.  It's the only way that you can show her that she is doing what you are asking for. 
 As she gets better at it and it becomes easier for her, then go a bit further.  Do not work for speed at first! Good luck!  I believe you will do a much better job than your trainer.

Nancy Cade