Try and pick your sweetcorn as close as possible to the time you're going to eat it. That way you can enjoy all the delicious natural sugars before they start turning to starch. If you can't eat it straightaway, store in the fridge, but try not to leave it there more than a day.
Fresh tender sweetcorn on the cob needs very little cooking at all. Strip off the husks and drop into boiling water. Cook for 4-5 minutes once the pan comes back to the boil and serve with plenty of butter.
Instead of plain butter try this. Take some soft butter at room temperature and mix into it one finely chopped chilli, seeds removed, a squeeze of lime juice and some finely chopped coriander. Mix well. Form into a sausage shape and wrap with foil. Put in the fridge to firm up. When you want to use, unwrap and slice into 1cm thick discs to dab over the freshly cooked sweetcorn.
It's best to soak the sweetcorn in a bucket of water for an hour before you start cooking to get the husks nice and moist. This protects the kernels from the intense heat of the barbeque and creates a steamy atmosphere to gently cook them. The corn is ready when the husks are well charred.