Get aimed at the eyes while the lens is wide open...when you get focus lock very carefully, without removing your eye from the viewfinder, stop the lens down to 4 or maybe 5.6. Know what the shutter speed speed at whatever stop is going to be and set it there in anticipation of your f stop adjustment...the idea is to keep the camera movements to a minimum. Breathe in and pause for a second after you exhale. Use the fatty part of your finger rather than the tip to fire the shutter. Then you can take another breath.
Get off of the wide open 1.8 stuff. You'll be surprised what 4 and 5.6 will do. A dog typically has a long face so you need the room. 1.8 will NEVER give you the room you need. With this shot you were in real tight and really sort of pushed the lens beyond it envelope. Back off and stop down and I think you'll be impressed with what you come up with there. His whole mug will be razor sharp and everything else will be soft. Once you blur the edges of his ears and get the exposure to where it is just shy of being overexposed you'll have a keeper then.
Now you will hear it said time and time again that 50 is uncomfortable on a DX body. I have even said it myself. And it is true too! Here is the deal - as long as you don't try group portraits or things that are big like cars you can use the 50. The situations that work are half body portraits of a single soul (or almost up to bust type stuff) or details on a car or close range landscape stuff like a tree for instance.
