# Barista Guides | Espresso Basics
PULLING A SHOT
- Remove the portafilter
- Purge the group head with a small amount of water, this gets rid of any coffee grinds or oils sitting on the shower screen
- Knock out the previous coffee puck sitting in the basket
- Wipe out the basket with a clean, dry towel
- Grind and dose the coffee
- Distribute the grinds evenly in the basket
- Tamp evenly
- Wipe the rim of the filter basket and edges of the portafilter to remove any free coffee grinds
- Insert the portafilter into the group head and brew
- Remember to keep the coffee evenly distributed in the basket and to tamp evenly with a straight arm
When hot water comes in contact with ground coffee it begins what’s called extraction. This is the process of extracting flavour compounds from the dry coffee and dissolving them into hot water. All coffee beverages are part water, part dissolved coffee.
When dialling in, it's best to start with a dose that will always remain the same. Then get the type of flavour right by balancing under & over extraction through manipulating your yield. Then work on getting the desired intensity of flavour by grinding finer or coarser to manipulate your contact time.