Sometime last year I read in a book a description of counter-steering and it made no sense to me. Something about leaning or steering one direction to go another. I couldn't figure out what they meant. So I filed it away. I read the description again and suddenly it made sense, you just push/lean on the handlebars in the direction you want to go. The bike leans over automatically and you turn. But I wasn't sure why they called it counter steering - maybe because your body wanted to lean the other way and acted as a counter weight? Anyways, I was having fun on my Marin and my newfound technique, gliding through the corners on my way to work.
It turns out all I did was discover that thing called "steering".
In Issue 17 of Bicycle Times there was another description of counter-steering in the Between the Lines column about moving hazards. They described how to make a quick turn - "to go right, you first need to flick your handlebars to the left. This is known as counter-steering, and it causes your body weight to shift to the right. As soon as that happens, steer sharply to the right". Whoa, what? Kinda shook my bikey world view.
So I gave it a try, practicing on my commute. There are some 90 degree turns to and from work where I'm going slightly downhill and picking up speed. I often end up taking these corners a bit wide, which isn't good if I drift on into the oncoming traffic lane while making a right turn or into the curb while turning left. I don't need to steer too sharply on these corners, but after trying the real counter-steering a few times I started getting the idea. And whaddayou know, it works.
In issue 19, a Bicycle Times reader (also a motorcycle rider), wrote in to try to clarify counter steering, pointing out that it's more of a push on the handlebars. But his description was also a bit confusing so I turned to Sheldon Brown and found his take on Counter-steering in his glossary here which I wish I'd read in the first place. I'll just copy and paste for your reading convenience, since I know how busy you are:
"When a bicycle turns, it must lean into the direction of the turn so that the tilt of the bicycle and rider counterbalances the "centrifugal force" created by the act of turning. In order to turn left, you start by turning the handlebars to the right for a moment. This moves the front wheel out to the right of the center of gravity, so the bike will start to fall to the left. This is immediately followed by turning the handlebars to the left to cause the bike to remain in balance, which also creates the desired left turn. "Countersteering" refers to the momentary motion of the handlebars in the opposite direction of the desired turn. usually, this is accomplished through the normal slight weave of the bicycle to maintain balance.
Some people, particularly motorcyclists, make a big deal out of this as if countersteering is some special advanced riding technique that you must learn to become an expert bike handler. It isn't. It's just a fancy sounding name for the normal process by which any two-wheeler (or even a unicycle) is controlled.
However, to be ready to swerve quickly out of danger, it is useful to practice quick, forced countersteering so as to initiate a turn as quickly as possible. The amount of countersteering needed decreases as speed increases, and practice will teach you how to approach the limit of traction without exceeding it and skidding out. See also my article on braking and turning."
So it's nothing real fancy, just a normal way to turn a bike. I'm having fun with this newfound technique and don't use counter-steering for every turn, but find it comes in handy. Seem to do it unconsciously sometimes - probably learned it as a kid, along with most every other biker.