For a consistent V60, start with the ratio: one part coffee to fifteen of water, for example 20 g of coffee and 300 g of water. You can go from 1:13, fuller, to 1:16, lighter, but fix a starting point and change one variable at a time.
Use a medium-fine grind and water between 92 and 96 °C. Bloom with twice the coffee's weight in water and wait 30 to 45 seconds. Then pour in stages until you reach the full weight, in about 2 min 30 s to 3 min overall.
If it tastes bitter or dry, grind coarser. If it tastes sour and thin, grind finer. Adjusting the grind before touching the ratio gives you a cup you can repeat tomorrow.