Prepare the crumbing station in three shallow dishes, first flour with salt and pepper; second whisked egg and milk; third breadcrumbs.
Dip each piece of calamari in each of the shallow dishes (flour, egg mix, then crumbs), then place on a single layer on a plate or tray and place in the fridge while you prepare the oil. This also helps to crumbs set.
In a deep frypan (or in a saucepan) add enough oil to create a depth of 2cm and bring to a hot temperature, about 180 degrees C. Add the calamari rings one at a time in batches that ensure there isn’t too much crowding. Turn as/if required to ensure brown on both sides. When cooked remove from the oil, rest in a place where any residual oil can drain and do the next batch until all cooked.