The porta-filter is the entire assembly of the handle, the basket, and the spouts. The porta-filter is always made of metal and must always be warmed before extracting espresso. If you see the porta-filter resting on the tray of the espresso machine at your local coffee shop you should walk out the door. Pre-heating the porta-filter can be done using the hot water nozzle or water from the group head itself. It is not recommended to ever use more than 1-1.5 ounces of water at a time since excess use will cool the hot water reservoir inside the machine. It is essential that you learn how to "temperature surf" on your machine to accurately control the temperature at which the espresso is brewed. Some people recommend leaving used pucks of espresso in the basket to help maintain heat. This advice seems advantageous, but make sure you allow about 1 oz of water to flow out of the head to rinse the screen after pulling each shot.
A note on cleanliness: Although most porta-filters are black inside, they are supposed have a shiny metallic surface. After one day of not cleaning the porta-filter coffee oils will accumulate, go rancid, turn black, and ruin any shot your prepare. If your espresso comes out thin, white, and rancid tasting this is usually the problem. Although most people think it is impractical, I believe it is important to clean the porta-filter, basket, and screen heads hourly. To clean these components use tri-sodium phosphate (TSP) or Puro Caff and use a 1 inch square piece of a green brillo pads. Scrub thoroughly, but quickly to avoid cooling too much, and rinse thoroughly. While scrubbing the porta-filter, back flush for 30 seconds with the blind basket in place and a teaspoon of TSP for 30 seconds, and follow with at least 5 rinsing cycles. If you have never cleaned your porta-filter before, place it upside down in a milk pitcher, fill the pitcher with water covering only the metal, add a couple teaspoons of TSP, and boil the water using the steam wand. Scrub periodically. This should get out the worst rancid coffee oils. If all else fails order a new porta-filter.
The steam wand ejects steam in order to froth the milk. The steam wand should be cleaned after it is inserted into milk and at the end of each day. Do not allow the steam wands to soak in water overnight since some of the dirty water can be sucked into the boiling tank inside the machine.
With a semi-automatic espresso machine, the keypad can be used to push a predefined amount of water through the coffee pellet. The keypad is easy and useful, but is not the best way to determine shot size. It is essential to watch the shot brew and stop the flow of water before the crema turns pale in color. This pale color crema deteriorates the crema already present in the cup and ruins the delicate flavor. Typically, there is a on/off switch next to the keypad which should be used instead of the keypad. Typical shots are 1-1.5 ounces, not the 2 ounces that you are normally served.
Tray The espresso tray is used to catch excess water, to pour out drinks, etc. It should empty into a drain. If the espresso tray does not have a drain, make your own by drilling a 1/2 inch hole in the tray, attaching the appropriate fittings, and then running a high temperature hose to the sink. The tray should be cleaned each day with a sponge to remove excess grounds.
The boiler pressure gauge on most espresso machines measures the pressure of the water tank as well as the pressure that is forced through the espresso. The pressure for brewing should be between 9 and 10 atmospheres. The espresso machine pressure has the essential role of forming the aromatic and volatile crema, and without this component, espresso would only be strong drip coffee.