You said that you have trouble getting the whole subject in focus… Generally, in a case like a portrait or a situation where you have something in the foreground and some extraneous detail in the background, you are better off using a shallower DOF, like happened in your dog photo. Your dog has a great face, and the fact that the hindquarters are out of focus moves attention to the face.
It can be a challenge getting the focal plane where you want it, for sure, but it generally makes for a more technically pleasing photo. Extremely shallow DOF can give you what the Japanese (and mostly everyone else) call ‘bokeh,’ where you get circles in the background that give artistic flair to the photo.
There’s an example of extremely shallow DOF… I actually took this at F/1.8 but with the lens on the camera backwards (for macro goodness) and had to focus manually by moving the camera away and toward the subject.[/img]