>>7750816
It's a somewhat messy and personal method.
I use the vertical and horizontal reference lines to define the middle and the start of the pelvis, which should be the same height and width, then I connect the pelvis to the ribs by drawing the core, continuing with the legs and buttocks where the widest point meets the horizontal line, which should clearly be wider than the shoulders.
I do a lot of guessing and rely on experience if something looks strange or ugly, try to change it. You can also play with the height of the pelvis to make it more attractive on thin bodies with small breasts for example.
When I have to draw more complicated poses with perspective, I remember what David Finch said and draw the pelvis like 3D underwear as a reference.
I watched a lot of mikeymegamega tutorials in the beginning too.