In carving a turn, not only must you have all your weight on the donwhill (outside) ski, you also must apply pressure to it.
What's the difference? If you lifted both poles and the inside ski off the snow, you would have all your weight on the downhill ski. There would be pressure as well, but not much.
To increase the pressure on your ski, you must push it into the snow. Push straight down as hard as you can, as if you were trying to push the whole length of the ski at least six inches underneath the snow.
Picture yourself jumping as high as you can: you drop into a squatting position, extend your legs and push as hard as you can off the floor.
In skiing, when you apply pressure to the downhill ski, you do somewhat the same thing, but without straightening. You drop into a low position by pushing your knees forward, dropping your hips back and leaning forward slightly with your upper body. Then you push as hard as you can straight down against the skis with as much force as possible, but you stay low.
Once you've finished the turn, you release the pressure and move into a more upright position. This is called unweighting.
The tighter a turn you wish to make, the more pressure you must apply. The amount of pressure exerted is determined by how hard you push and the strength of your thighs. Many skiers can't exert the necessary pressure because their legs aren't strong enough. You can develop strength in the thighs by sitting against a wall (back flat against the wall), with thighs parallel to the floor. Work up to 10 minutes in this position. Knee-bends are also good exercises; you should be able to do 35 to 50.
Next: low body position