Quick Step should be a sharp and purposeful movement. Every 3rd step requires you to cycle through with what I like to call a quick step. Focus on driving the knee upward while getting your foot off the ground as quickly as possible. The steps in between the quick steps are simply taking the heels off the ground. Most people have the tendency to clench their fists and grind their teeth when performing drills such as this. Stay tall and relaxed. It helps if you think like a sprinter for this drill.