Espresso machines work on the basis of forcing pressurised boiled water through a "puck" of ground coffee creating a thick and concentrated liquid. The Italian Angelo Moriondo patented the first espresso machine in 1884,  but it has been over the last 50 years that espresso has been considered the best way to brew and drink coffee.  Espresso machines are synonymous with the cafe culture that originated in Italy and has now spread all over the world. Almost all restaurants and cafes have their own espresso machines and now the Americanised fast food chains have even started to get in on the act. During the eighteenth century the combining of coffee with milk became an enjoyable practise  and espresso machines are suited for the milky connoisseur of coffee drinkers, that prefer their flat whites, cappuccinos and lattes. The guide below is from Intelligentsia Coffee.
Fresh coffee beans
Coffee grind scoop
Step 1: Clean and dry the coffee basket to remove coffee grounds and residual oil from previous use. A clean dry cloth will work well.
Step 2: Grind coffee and add to the coffee basket, the strength of the coffee will depend on how much you add to the basket.
Step 3: Level the coffee grounds in the basket using your finger or a tool. This will create an even density and allow the water to run through the coffee bed evenly, producing an even extraction. A uneven extraction rate will cause the coffee to acquire a dry, bitter and unpleasant tone in the final flavour.
Step 4: The next step is tamping the coffee bed using the tool on the espresso machine or a hand held one. Tamping is important to achieve even pressure across the surface of the coffee bed as well as creating a level puck. The key is to apply consistent pressure to generate even extraction. If the puck is uneven water will pass through at different rates and extraction levels will be inconsistent. Applying too much pressure will also lead to an uneven level.
Step 5: Flush the grouphead of the espresso machine before adding the portafilter as this primes the the boiler to bring fresh water to the front and cleans the screen of any old coffee.
Step 6: Insert the portafilter that contains the coffee basket into the group head. Be very careful not to knock the portafilter in the process as this will disrupt and break up the coffee bed seal.
Step 7: The initial streams of water coming through the portafilter will be thin and very dark in colour. As the shot progresses the streams will get thicker and lighter. When the streams turn transparent it is time to take the cup away from the machine as the coffee is no longer dissolving any desirable flavours.
Step 8: Once the portafilter has been removed, knock out the espresso puck, wipe the basket clean and again flush the group head to prepare for the next use.