At its best:
Having tended your sweetcorn crop all summer, make sure you harvest the cobs when they're at their peak of ripeness. Pick them too soon and they'll be watery and not very sweet, pick them too late and they'll be tough. Harvest times vary, depending on the variety, the sowing time, the weather conditions and the part of the country in which you live, so check the ripeness of your cobs regularly.
Keep a close eye on your sweetcorn cobs as they swell. Once the tassels have turned brown, test for ripeness by peeling back the outer husks and pushing your fingernail into the cob. If a milky solution comes out, then the cob is ready to pick, but if the liquid is clear, leave it a little longer.
Pick the cobs just before you're going to eat them, with water on the boil ready to pop them straight in. The sugars in sweetcorn start turning to starch the very moment the cob is picked, so freshly harvested cobs have a sweetness you'll never get from shop-bought ones.
If you have a glut of sweetcorn, you can freeze it. Blanch the cobs in boiling water for five minutes, cool in iced water, then strip off the kernels and store in freezer bags.