I've learnt now, use minimal smoke, a non at all, and stand further back to look at the frames. Don't look for individual bees, just the general movement. Her tail makes a sort of swooshing movement as she walks. It's quite distinctive once you see it, and the long pointed tail.
Once you find her, even if you don't mark her, it's worth watching her for a while, just to learn how she walks, where she goes on the frame, and how the other bees act around her.