There is a misconception that the word “espresso” implies a certain type of roast or bean. Although some coffee roasters do create roasts that they label as “espresso,” the brewing method is actually what makes it so.
1) Choose the appropriate grind.
The important thing to remember is that the coffee MUST be ground very finely. Steam is forced through the ground coffee and if it isn’t ground finely enough, the steam does not properly absorb the flavor of the coffee.
2) Use fresh, clear and clean cold water that is free of impurities.
The quality of your espresso beverage, as with all brewed coffee, is heavily dependent upon the quality of the water that you use. Your own freshly drawn tap water is fine; however, if you're not happy with the flavor or color of your tap water, you should consider filtered or bottled water for brewing.
3) Tamp your doses accordingly.
Tamp your grinds flat with 30lbs. of pressure, rotating the tamper to ensure a level surface for even distribution of water.
4) Timing really is everything.
For a double shot of espresso, which is what is most often brewed, 2 oz. should be brewed in 25 seconds. If it takes over 30 seconds, the coffee will be over-extracted and bitter. Start over by tamping the grounds a little less or coarsening the grind a bit. If your espresso brews in less than 22 seconds, the taste will be thin and uninteresting. Start over by tamping the grounds a little firmer or increase the fineness of the grind.
5) Clean your equipment after every use.
Coffee oils quickly build up and, over time, become rancid. These rancid oils will taint your coffee's flavor, and possibly damage your machine.