First and foremost, it is important to preheat the machine before using it. This machine is a single boiler machine and heats up very fast. However, you want everything to be hot, not just the boiler. It is recommended to have the machine on for 20 minutes before using it. This will ensure that the portafilter, brew head, and everything else is hot. If the machine is not hot, the shot will be cold, which will affect the taste of the coffee and make it sour.