1. tamp evenly so that the base of your coffee grounds are level and not running up (or down) hill.
2. use a consistent downward force. Ideally around 15kg of force (you can tamp on to a set of bathroom scales to get an idea of what 15kgs feels like to you).
3. dont knock the side of the basket with your tamp after tamping - it can create a fracture in the coffee puck through which water can channel through during extraction, reducing the goodness in the cup.
Be consistent and repeat whatever your technique is each time. If you tamp with 1kg of force, thats okay, you will end up grinding finer to compensate or if you are he-man and force too much pressure on your tamp (every time), you'll end up grinding more coarse, again, that's OK - its all science and experimenting with differences is fun!
Personally, I tamp lightly and prefer a finer grind. I do tap the basket on the counter half way through my dosing to settle the grinds too.
If you have any questions, please contact me, or leave a comment below.