In order to keep your camera level during operation, you'll have to properly balance the Steadicam system. There are two separate planes you'll have to consider when balancing: the vertical balance and horizontal balance. As you adjust one, it might slightly affect the other, so you'll have to continually adjust each in order achieve perfection (or something close to it).
Hold the Steadicam unit sideways, supporting it by the gimbal. The unit should swing freely. If the camera lowers itself, you'll have to add a counterweight and add an inch to the arc distance. If the Steadicam lowers itself quickly, remove a counterweight and reduce the arc distance. The goal is to have the Steadicam fall slowly when you tilt the unit on its side. This is known as vertical balancing.
To achieve horizontal balance, keep the Steadicam upright with the handle vertical. If the unit tends to fall forward or back, use the long blue trim control to make an adjustment. The shorter trim control can be used to prevent it from falling to the sides. Once you've adjusted these trim controls, test the vertical balance again.
Despite what the name might imply, a Steadicam will not magically make every choppy movement you make invisible to the camera. You'll have to practice balancing the Steadicam unit and supporting it as you move. To learn this technique, practice with a cup of water.
Hold the full cup in front of your body, and think of your arm as a shock absorber. Bend your arm slightly, and hold your elbow out to the side. Walk forward at an increasingly brisk pace. Keep the cup moving through the air in a straight line, using the natural motion of your arm to absorb the impact of your steps. This is different than the way most people would hold a water cup---close to their body and lower.
Apply this same movement technique to a handheld Steadicam. Ignore your instinct to hold the camera close to your body, and instead let it rest in front of you as you move. Your shots will look better, and your mind will be free to concentrate on proper framing, as well as avoiding obstacles.