The subpubic angle is much wider in females than in males,
typically more that 90 degrees and less than 90 degrees, respectively.Sex determination is only really possible with adolescent or adult skeletons because there is not much sexual dimorphism in preadolescent children. One of the common ways to determine sex is using the size of the bones; males tend to have larger bones than females. Males also tend to have larger areas for muscle attachment.
The pelvis is one of the most common bones to use if it is
available. The subpubic angle is much wider in females than in males,
typically more that 90 degrees and less than 90 degrees, respectively.
The greater sciatic notch is also wider in females, usually more
than 68 degrees for females and less for males. The acetabulum, where the head
of the femur meets the pubic bone, is typically larger and deeper in males
than females.
The sacrum is straighter in females and more curved in males. The
space in the middle of the pelvic bone (the pelvic inlet) is larger in women to
facilitate birthing.
The cranium, or skull, is another useful bone for sex determination. The chin of males tends to be more square and tends to come to a point in the middle on females. The frontal bone (forehead) of males tends to be slanted back and on females it tends to be more rounded. Males also tend to have brow ridges above the eyes more than females.
There are other useful bones, and other things to look for, however these are the most common ways of determining the sex of a skeleton.