To prepare an espresso shot, you will need an espresso machine and freshly ground coffee beans. Here are the steps:

1. Start by warming up the espresso machine, which involves turning it on and allowing it to heat up to the optimal temperature.
2. While the machine is warming up, grind your coffee beans to a fine consistency, ideally using a burr grinder.
3. Fill the portafilter basket with the ground coffee and tamp it down firmly using a tamper.
4. Lock the portafilter into the espresso machine and place a preheated espresso cup under the spout.
5. Turn on the machine and let the hot water run through the coffee for about 25 to 30 seconds, until the shot glass is filled with about 1-1.5 ounces of espresso.
6. Stop the machine once you have extracted the desired amount of espresso.

It is important to note that the quality of the coffee beans, the grind, and the pressure used in the extraction process all play a critical role in the taste and quality of the espresso shot.