Getting better results with the Puppet Warp tool?

2. Is this tool designed to make very subtle changes to an image or is it realistic to expect big changes to the composition of an image with it?

The result depends on subject, lighting, intended transformation …

In CC 2014, I'm not getting realistic looking results when using the Puppet Warp tool.

Could you please post before and after screenshots to illustrate your problem?

You are not wrong.  Puppet Warp is a bit like Refine Edge in that it is not as intuitive as some of the tutorials would have us believe.  I still struggle with it.  All I can suggest is picking the best tutorials by going to Adobe TV

http://tv.adobe.com/videos/puppet-warp/

If it is going wrong, rather than trying to make the most of a bad job, start again with better pin placement.  If you still end up with what looks more like a boneless string puppet than a real person, use tools like Liquify to put things right. Run a work path around the perfect outline, and use that to make a selection from which to use the clone tool to fix inside the mask, and a layer mask to fix pixels that have strayed outside the ideal profile.

Lots of PW pins are good for anchoring the bits you don't want to move, but less pins are better for the bits you do want to move.  Look at photographs that approximate your intended new shape, and use them to work out how the rest of the body (if that's what you are warping) would interact/react with your new shape.  Or just mime the action yourself, and see where your other limbs, and the rest of your body should look.

You have to provide a screenshot/ low-res version of your image. Nobody can advise based on such generic questions.

Mylenium

but as a result of doing this, it seems to affect the rear of the elephant.

Not surprising.

To fix items that are not intended to be affected one should put some pins in at the beginning, in this case a couple of pins in the head region should help.

You want think of the pins as thumb tacks. You are tacking down ALL of the bits you don't to move.  For this image, tack down the whole body. Not too many pins - that is bad. Your spacing looks good.

I would start by rotating the second from the top and work my way down...