Slippery surface? Don't plank on your socks. This will make you slip and will increase the risk of injuries. You can plank on bare feet, but this is painful for some people. Wearing sports shoes is your best and safest option to execute the plank.
Look diagonally forward, to the ground, and slightly tilt the pelvis backwards. This way your body is one straight line from your feet to your head.
Engage your whole body. It's important to contract your back, arm, leg and abdominal muscles when doing the plank. This way you prevent retracting the shoulders too much or hollowing your back.
Breathe calmly. This sounds logical when you read it... but you can't imagine how many people hold their breath during an exercise. Especially when doing strength exercise people often forget to breathe.
Do this exercise in front of a mirror. This way you can check if you're in the right position and how this feels. You want to enjoy all the benefits of this exercise, which is why it's important to use the right technique!