First of all you need to take note of the word ‘clean’. You must ensure that your equipment and utensils are clean. The water should be fresh and filtered, if possible, as regular tap water can taint the final cup. It's a good idea to get in the habit of cleaning the machine and porter filter regularly after use and between shots.
Fresher beans produce a better espresso, which should be viscous and full of flavour with a good crema. A bad coffee will be thin and flat-tasting.
