While moving keep the knees open wide, at least over your ankle or slightly wider. Don’t let tension fall out of the band, even while you step. If you find that you lose tension, avoid bringing your feel all the way together on the step. Take a huge step with your outside leg and then a smaller step with your inside. Avoid throwing the outside leg out violently. Lastly keep the chest up the entire time.
If walking forward an back, envision walking on railroad ties. Don’t let the band pull your feet or knees together.