1. Fix the dose
Start with 18 g of coffee in a double basket and weigh every dose.
2. Choose a ratio
Aim for about 36 g of espresso in the cup, a 1:2 ratio.
3. Time the shot
The shot should take 25 to 30 seconds. If it runs faster, grind finer; if slower, grind coarser.
4. Taste
Sour and thin means under-extracted: grind finer or increase the yield. Bitter and dry means over-extracted: grind coarser or reduce the yield. Change one variable at a time.