If your soil is heavy clay, now is a great time of year to dig it over – just roughly, leaving large clods of earth exposed to the elements. The good news is you don’t need to do anything else. Winter frosts will break those clods of earth down into a fine tilth; one of nature’s miracles.
Another way to improve your soil is to sow what are known as ‘green manures’. These are crops which will grow and keep the soil covered over winter, stopping rain washing away that valuable nutrient rich top covering of soil.