Both of mine will put their tail up if aroused. If another dog is outside the fence, if they are "alerting" to something.
When they are "up" in drive, doing agility, chasing the frisbee or ball, or training, the tail is usually held level with the back, sometimes wagging. When Rumor is anticipating the ball throw she will duck down in a play bow with the base of her tail held level with her back and she lets the last half of it droop and wag. It's odd looking. Almost like when dogs do the "tuck butt and run really fast".
When they are serious the tail is down, with a slight curve in it. This is usually when working livestock.
When just walking around Rumor's is usually never held above level with her back, and Zen hold his with the base level with his back and the tip curved upwards, usually wagging.