i usually start off with a lighter tone to make the formation of the creases and cracks , then move on to a darker shading and finish with lighting. this is a fine tutorial, however i think you over did it a bit with the lighting
Oh man, I'm in love with your other tutorials and arts but I'm a bit wary of this particular one :S I really wouldn't use dodge and burn to colour as you never have any control over the colour of the lighting and shadows (as you can see here, it's made the light white... light on an object is never pure white and it looks odd). You're going to need as much control over the colour as you can, so dodge and burn is kind of a big no-no for painting
Also, I think maybe you should have pointed out where the rock interacts with the environment as the shadows just seem to be a darker shade of the midtones (light doesn't work like that). It would alter depending on the weather and time of day, but the shadows would most likely have a blue tint to them (it'll make it pop, trust me ^~^). Although looking at your other works, I reckon you know this because you have a great grasp on colour in your other pieces
But yeah, keep up with your awesome work! I'm a "silent" fan haha.