Ideally, you should start preparing the soil about six months or more before planting grains. Any sod should be removed or tilled into the top 6 inches of soil. After tilling with a tractor or rototiller, plant peas, beans, fall rye, or another green manure crop to help break up the soil and improve fertility. This crop can be tilled back into the soil once or more. Till once more just before planting your grain seed, to discourage any weeds.
Wire worms are a major pest, especially in newly-tilled pasture: they live the good life in the roots of grass plants, and will head straight for your grain when it's planted. Island farmers have lost entire grain crops to wire worms. One organic (but not guaranteed) solution is nematodes, which can be sprayed onto the soil once the weather is warm enough. Generally speaking, if you have diverse, healthy soil biology then there shouldn't be an overpopulation of any pest, including wire worms.
We (Makaria Farm) planted grain in recently tilled pasture in 2009, and saw little if any wireworm damage in our grain crops. The wireworms may have been distracted by the neighbouring potato fields . . .