I'd make the tail look like it has more weight. Somthing like a slightly delayed up/down 'wave' like motion that's sympathetic to the up/down motion of the hip. It's hard to explain, but this creature is suppose to be fairly large, so it would be using it's tail for keeping balance of it's back end. Maybe somthing similar to cracking a whip, but not too pronounced. Also... Animals with long necks, kind of 'throw' their heads toward the direction they step. Think of how a Giraffe would walk, leading with it's head.