Start with a lightly drawn cross, similar to a lowercase "t." The vertical line of this cross should represent the middle of the torso, running along the breastbone. The horizontal line represents the shoulders at their widest points.
Encircle the upper section of this cross frame, creating a circle or oval with an even circumference that touches the upper tip of the vertical line and both ends of the horizontal line. This represents the chest.
Draw a more angled shape that borders the cross and oval that also extends downward to complete the shape of the chest and waist. Depending on your character's build, this should look like a rectangle to trapezoid for men, while women are curvier.
Add a small circle at each of the upper points of this torso shape to represent the shoulders. Draw long stretched-out oval shapes to represent the thighs and upper legs.
Draw along the torso frame you've created in darker lines to "flesh out" the torso and give it its full shape.