The final product of any endeavor is heavily reliant on the skills, knowledge, and tools of the craftsman, and the perfect espresso is not an exception. Traditionally, the Italian rule of the 5 M's creates a sound set of requirements that guides the barista to the perfect espresso. 

1. Miscela (Espresso Blend)

While it is possible to make a bad espresso from a good blend of coffee, it is impossible to make a good espresso from a poor quality blend. Ultimately, the blend you decide on comes down to personal taste, but the blend should be both fresh and of high quality. 

2. Macinadosatore (Coffee Grinder)

The grinder should be of high quality and the blades must be changed regularly. The consequence of blunt blades is burned coffee grounds. Finally, for the best results, the coffee should be ground immediately before use.  Once ground, it has a larger surface area and is more vulnerable to oxidization.

3. Macchina Espresso (Espresso Machine)

Even though a good espresso machine is not necessarily required to make good espresso, consistency and reliability come from good machines. Additionally, it's important that the machine is maintained at the right temperature and pressure. Cheaper machines are much less consistent with their production, causing the barista to rely on a bit of luck, a concept few business owners are comfortable with. 

4. Mano dell'operatore (Skill of the User)

The skill of the barista comes with an understanding of the machine operations, knowledge of the final product, and practice. It takes time to become comfortable with a new machine and the intricacies of using it.  

5. Manutenzione (Maintenance)

Finally, the outcome of a single espresso is heavily dependent on the routine maintenance of the machine itself. For the best results, a machine and grinder should be regularly cleaned to prevent the build up of stale grounds that can contaminate fresh coffee.