Fixie Braking Technique

Since fixie braking is more involved, you'll need to remain extremely aware of your surroundings. Constantly scanning the road for hazards is ideal while riding through traffic, but you'll have it a little easier while practicing. Try to define an ideal stopping point in your practice area by setting up goal markers like traffic cones. With a definitive "red zone" to work with, you'll be able to practice stopping short of (or even skidding around) obstacles.

Despite all the inherent danger, there is some good news. When it comes to slowing down, fixed gear riders have a few different choices. Each comes with its own set of pluses and minuses (as well as ideal riding conditions), so it's wise to learn at least a couple. The two most common are:

Pace Pedaling

Decreasing the speed of your pedaling is the easiest ways to slow down a fixie. Since the rotation of the rear wheel and the movement of the pedals are directly connected, slowing down your strokes will put a damper on forward motion. In non-emergency situations this should bring you to a smooth, natural stop -- time/distance permitting of course.
While ideal in typical riding conditions, a disadvantage to this method is that if you try to stop very quickly, the pedals will simply continue to turn, bouncing you up and down. This typically happens when you are afraid of hitting something, can cause loss of control, and is very ineffective at slowing you down.

Skid Stopping

Is "danger" (or "speed") your middle name? Then the skid stop is probably more up your alley. The process is started by leaning forward on the bike and relieving the weight on the rear wheel. If you have the balance to lift the rear wheel ever-so-slightly off the ground, even better. Once the traction of the rear wheel has been taken out of the equation, use your feet to lock the pedals in a horizontal position. Push down on the pedal coming up, and pull up on the pedal going down (this is why being attached to the pedals is important). This should slow the suspended rear wheel to a stop. Shifting weight back onto the rear wheel should cause the rear tire to skid, causing the bike to slow to a stop.
Skidding on the rear wheel will stop a fixed gear bike more quickly than pedal pacing, but (obviously) can damage the tire (even causing flats with light tires). In slippery conditions, pedal pacing may actually allow you to stop more quickly- optimal stopping power actually occurs just short of a skid.

Using Brakes

A sure fire way to stop a fixed gear bicycle (or any bicycle) is to apply smooth and gradual pressure to both brake levers, bringing the bike to quick, short and safe stop. In situations requiring a rapid stop, almost all of your stopping power comes from your front brake, so mounting only a front brake is an acceptable compromise. Some track bikes don't have mounting holes for rear brakes, but at the very worst you can get a fork that allows for a front brake.