The old saying ...begin with the end in mind... holds true when making the perfect espresso. The goal is to extract a rich clean cup of available coffee oils that are on offer from the roasted beans. So how do we do this?
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.