When shopping for corn, begin with a visual scan.  It should be bright green with dark brown silk (that hairy stuff at the top).  The ends, where it was attached to the stalk, should be pale and moist (not brown and dry).  Now feel the corn (be one with the corn *insert eye-roll here*).  Grasp the ear in one hand and give it a few gentle squeezes from bottom to top (this one's gonna haunt me, I just know it).  You can feel the bumps of each kernel under the pressure of your thumb.  You are checking for patches of undeveloped kernels throughout the ear. 
 
At the top, you are checking to see if the plump kernels reach the very tip.  And if they don't?  It just means that at some point during fertilization there was a momentary interruption in the process and there is now a nice place for you to rest your buttered-up fingers while you eat the remainder of the ear typewriter-style.  As much as we all hate interruptions in fertilization (ba dum bump), they are a natural occurrence and the resulting corn should not be looked upon as faulty or inferior in any way. 
 
Next, give the silk a gentle tug. If it comes out easily, there may be a worm inside enjoying the sweet, tender goodness within.  Did you know?  Each strand of silk is attached to a kernel of corn!  If a critter has nibbled the kernels, the silk has been broken - and that is why it would come out easily.
 
If you plan to eat your corn that day, just refrigerate it in the plastic bag in which you brought it home.  Otherwise, soak the ears in cold water for a few minutes, then return to the bag and refrigerate.  Sometimes they dry out at the market (wind, sun, exposure in general) and maintaining their moisture and cool temperature is imperative to having a great tasting ear of corn.  The worst thing you can do is husk the corn at the market and store it for use later as the flavor suffers greatly.  Sure, supermarkets do it - but their corn isn't the same. 
 
What you see at Bialas Farms' stands is SE or sugar-enhanced corn.  It's not a Super Sweet variety.  We use several varieties, each with different growing times and physical characteristics.  The first corn of the season is almost always a little smaller - mostly because it has faced more climatic stresses than later-season corn.  It also has a shorter growing time (seeds are typically labeled with a number of days from sowing to harvest). 
 
Farmer Sonny plants one 'patch' of corn every week to 10 days from May until the end of July.  We get about 10 plantings in, and although we plant one section to be ready each market week, Mother Nature doesn't always cooperate.  Sometimes the corn is a little older or younger than some people prefer, but we feel it is most important to pick it fresh for each market.  Feel free to ask at the market if you aren't sure about this week's corn.
 
The big question is always, "when was this picked?"  We always pick our corn the day before a market (so, Thursday or Friday), usually in the late afternoon.  The contents of boxes (they are designed to hold about 2000 pounds of onions, so you can imagine how large a box this is) are dumped into a huge tank of icy cold well water.  After a thorough soaking, the cobs are laid into crates, the crates are stacked, and the entire pallet of corn is rushed to our 38-degree drive-in vegetable cooler. 
 
As long as the corn has been handled properly, you really cannot tell the difference between corn picked that day or the day before.  In fact, I've eaten corn 3 to 4 days old and can barely tell - and I'm a veggie snob.  Although our SE corn isn't designed for long-term storage like a Super Sweet, it can last several days when stored in a cold and moist environment. 
 
Lastly, DO NOT OVERCOOK your sweet corn!  Everyone has their own cooking methods, and despite the debates, your method will always be the best.  And frankly, if that's what your family enjoys - go with it!  As for me, I pile the husked corn into a big stock pot, then cover with body-temperature water.  Covered, I bring that pot to a boil, then TURN IT OFF.  It's done. 
 
I'm a purist and use only real butter (Preferably a frozen stick, the paper wrapper torn down around one end a bit to reveal previously melted and refrozen butter with a stray silk or two stuck to it.  Ok, I really don't like the stray silk thing, but let's face facts - it happens.) and salt.  Run that stick of butter right along an hot ear of corn and watch the little beads of heaven accumulate within the rows of bi-color beauty.
 
 The Ontario Ministry of Agriculture has this very interesting fact sheet that discusses the various sweet corn genes and the characteristics of each type of corn.  It's dry and written for the industry, but easy enough to understand for a home gardener or corn aficionado.  http://www.omafra.gov.on.ca/english/crops/facts/90-126.htm