Some people said dog portraits are hard, however, with the right tools and patience, taking pictures with animals are fun!
To have the right tool, I would suggest to use of a flash light, higher ISO and a lens with a big aperture for a sharp and bright picture! This Picture was at ISO 400, a standard 50mm 1.8f lens with Flash on.
Tips:Remember to place the focus on the doggies eye, not the NOSE! unless you want some purposely effects.