1. Slow movement at the beginning. He brings one knee up towards the hip one at a time, and then repeating on the other side.
2. Picks up the intensity of the warm-up and started to jog in place.
3. He added different variations to the warm-up by doing high knees, butt kicks, jumping jacks, and rope reaches all with the same intensity.
These warm-up exercises that he demonstrated, in his video, are good for beginners. He includes the lower body and the upper body. He increases the intensity, so his heart rate is a little quicker, and he is getting the blood flowing through his body. What I would change all depends on what activity he is warming-up for. I would include, in my warm-up, exercises that are specific to what muscles will be used during the activity. I would also bring down the intensity, so the heart rate can lower before going into the stretching.
Good form and making sure you can talk during your warm-up.