corn on the cob? About 10 mins in boiling water or better still, if you have a microwave, wash it, put it in a dish or tupperware box add a tablespoonful of water and cover for 3/4 mins. it depends how you like it too. gernerally, if you poke it with a fork and it pierces the kerns quite easily then its ready.
Depends on how you like your corn on the cob. I like mine crisps and no hard shells so when you bite into it, it bursts with juices. For this I boil the water, add a bit of salt and then plunge the cobs down in the water. Once it's brought back up to the boil I only give them about a minute. I don't like my cobs dark yellow
Of course, everyone has their own preferences, but I've found that about 4 minutes in rapidly boiling water is about right... doesn't overcook it and make it mushy. I add a heaping tablespoon of sugar to about 2 quarts of water which is enough for about 4 medium sized ears...
I do mine in the microwave, I leave the last layer of the husk on, put it flat on the turntable, thin end to the middle and allow 1 minute and 20 seconds per cob. Mine is an 1100 power one. The cobs we get Down Under are about 7 inches long, not counting the beards. if you haven't got a microwave, try steaming, much better than boiling.