Grow carrots in the miscellaneous section of your rotation. They do best in a deep, rich, fine soil so some ground preparation (from around March) may be required, and using a good quality Top Soil product will help. Avoid freshly manured, stony or very wet ground. The first sowings undercover in a greenhouse or polytunnel can give you an early crop but do not be tempted to start them off too early outside. May is generally the best month.
If planting outside, sow seeds in a bed with fine, well worked soil undercover from May to August. Sprinkle the seed thinly into shallow drills and cover with fine soil or purchase a good Top Soil and add that. Thin the seedlings as they grow to leave a distance of 5 or 6 cm. Be sure to keep the plot free from weeds.
Early undercover sowings will be ready around July. Late maincrops will be ready from September onwards.