1.Set your shoulders back and down.
People often get pain in their shoulders when they do planks because they have their shoulders rounded.
2.If you feel pain in your lower back, lift your hips.
A great way to check your form is to practice in front of a mirror, that way you can see if your hips are too high or too low.
3.Want to feel it more, imagine pulling the floor apart with your elbows.
This is a great way of engaging your core even more.You aren’t actually going to move your elbows but just try to pull tight as if you are pulling the floor beneath you apart.
Give these tips a try and let me know how you get on