On the way down, it should be, depending on what she's wearing, straight down towards the abdomen for a tucked in shirt, a small deviation for a loose shirt, or for those bikinis, a curve in proportion to the top. You should use shading on the shirt. This is to reflect the creases in it. The abdomen should be slanting inwards as well, but remember, proportion's the word. Fill out the waist just above theabdomen, and this is where the legs start.
Belts also begin at the abdomen.
Shapely legs on a woman are a problem. Below the knee, the leg curves out three-quarters of the way, then slants inwards to the ankle. The thigh curves in at the back of the knee. The average shape from top of body to bottom should be that the body itself seems to stick out a little at the front, the calves and buttocks at the back, the shoulder-blades just a little further in. Arms are generally a simple affair, slightly rounded to reflect the muscle, slanting in at the elbow, then following the lower leg portion at the lower arm.