It's vital you get the grind right as this controls the rate of extraction, which in turn affects flavour. If the beans are ground too fine, a burnt or "ashy" flavour may result. If ground too coarse, the espresso will taste watery and thin, as the water will pass through too quickly without extracting all the flavours and oils in the coffee.
The coffee when you grind it should clump a little when you squeeze it (but not be too sticky) and be light and fluffy.
Clean and Dry:
Make sure there is no moisture (or old coffee grinds) in your porter filter and basket. If the coffee comes into contact with moisture, it could begin extracting too early. Use a tea towel to wipe the parts clean.
Fill the basket about three-quarters full with ground coffee. Tap the basket on your bench to "collapse" the coffee and ensure the basket is filling evenly. Add more coffee and collapse again until full, but not overly.
Tamp the coffee: Hold the tamper like a door knob and leans into it from above with a straight arm – about 15kg body weight is right. If you turn the basket upside down after tamping, the coffee should stay put.
After tamping, the basket should be about four-fifths full. If coffee sits too hard-up against the machine's shower screen, you may get an uneven extraction; too far away and the espresso may taste muddy.
Purge your machine by running some water through it before making your espresso.
Make the espresso.
In the first instance the machine will deliver drips before a steady stream of espresso. Fresh coffee will be slightly viscous and will almost look like honey pouring.
Extract roughly 36ml of espresso this should have a nice crema on top. This is the lighter, fluffier substance that sits on the surface. Crema looks like tiny bubbles and is reddish-brown or hazelnut in colour and dissipates after a minute or two. Lack of crema could be a sign your coffee beans are past their best.
A good rule of thumb is to work with: 18g of ground coffee in the basket, 36ml of liquid espresso poured in around 26 seconds.