The two types of corn are sweet corn and field corn.
Peak in the summer.
Check that the husks are fresh-looking, tight, and green. Avoid yellowed or dry husks. Strip back part of the husk to make sure tightly packed, plump kernels fill the ear. The kernels at the tip should be smaller. Pop a kernel with your fingernail to insure milky juice spurts out. Avoid kernels with watery liquid. The stalk should be green and moist. Avoid stalks that are opaque and white, or dry and brown. The silk should be moist, soft, and light golden. Avoid brown and brittle silk.
Refrigerate corn for up to 2 days if you must.