Whether you're picking the corn in your backyard, grabbing it from the farmer's market or the grocery store, you want to choose the best cobs possible.  If you have a choice, I like the variety with white AND yellow kernels.  I find them to have lots of natural sugars that are so yummy!  Then, pull a little bit of the husk down and look at the tip of the corn.  If it's mushy, pass.  If it's nice and yellow with well-hydrated silks, that's a great start!