“To accomplish all of this, we need to start with a rail system. And to my surprise, there are quite a few out there to choose from. But with a DSLR, there are special needs to handle the height and weight of the camera and all of its size requirements. This means that not every rail system will work with your particular camera. Rail systems designed for DSLRs are a little more height adjustable to allow for the height of the lens off the bottom mount of the camera. The more flexible systems allow for a battery grip or XLR audio box under the body too.
And as of the writing of this article, there are a few video-capable DSLRs on the market, but many more are coming. I am basing the article completely around my Canon EOS 5D Mark II.”
It outlines each of the pieces of the system you'll need and what they do. Very good read!
(Photo credit: snap from the cameradojo story)