Harvest the ears you set aside for seed about a month after the eating stage of your crop has passed. Pick the ears when the husks have turned brown. The harvest should take place on a dry day before frost.
Pull back the husks and lay the ears flat in a cool, dry location to allow the kernels to continue drying out. This location needs to be in an area where rodents cannot get access to the sweet corn.
Allow the corn to continue drying for two to three months.
Grip the ear between your hands and twist the kernels. Allow the kernels to fall into a bucket as they separate from the cob.
Winnow off any silk and chaff that falls into your seed container.
Remove any off-colored kernels from your sweet corn seed stash.
Store the kernels in a glass jar that rodents cannot get into, or store them in a paper bag and place the bag in the bottom of the refrigerator.