Identify a 15m (walk) or 20m (trot) or 30m (canter) square in your arena (set out cones or use other visual indicators for the corners). Then ride the square. Unsupported (not near walls) is best.
Repeat: 4 x each direction and per gait.
Appropriate Gaits: Walk, Trot, Canter
Optional Focus: 90 degree corners.
Optional Focus: flat sides.
Optional Focus: Manage how many strides each side takes.