Tamp to perfection
Taking into consideration the characteristics of water we know that the tamp should be consistent every time. In other words, knowing that water will always aim for the path-of-least-resistance, we know that if you make your espresso grounds perfectly tamped (perfectly level and the perfect amount of pressure), you will force the water to go through the entire dose of coffee.
If you can accomplish a perfectly level tamp, you will succeed in making the water touch every single grain of coffee in that dosage, and this will maximize the taste of you espresso. The perfect amount of pressure is important but as we just proved the perfectly level tamp is way more important.
If you tamp on an angle, a majority of the water will run through the lower part of the tamp leaving most of the flavor in the group instead of in your cup. Sometimes if you tamp this way, you will notice that the higher portion of the grounds is still dry.
