This is my least favorite part of the process, but having the right tools makes it a bit easier to get through.
Everyone has their own way of stretching canvas. I'm not sure if there is a "right" way and a "wrong" way, but some approaches are clearly more efficient and effective. (It's entirely possible that I'm not using any of those approaches.)
The most important tool in this group is the stretcher pliers (on the right). I always put a lot of pressure on my pliers, and in the past, I've had them break in half, under the strain. You get what you pay for--beware of cheap stretcher pliers. What you see here is an excellent, heavy duty model made by CS Osborne, that sells for about $40.