There are certain things you shouldn't do or at least avoid doing when trying to make good consistent coffee. In this video Jimmy discusses 3 mistakes in particular which we find are most common when we walk into a cafe for the first time.
The first mistake is tapping your group handle with the tamp after you've just carefully distributed and tamped the coffee. Why shouldn't you do this? You shouldn't because you will crack and dislodge the puck from the handle which will cause extraction issues.
Second mistake is to leave left over milk laying around in milk jugs that has already been stretched only to top them up with fresh milk and stretch it all again. Not only is it a health concern but it's also going to make your coffee taste nasty.
The last mistake is leaving your group handles out of the machine between coffees where they will get cold. This will change the temperature of the water as it passes through the coffee puck and alter the flavour of the extraction to it's detriment.