Naked necks are vulnerable. It's no wonder Dracula loves them.
Long "swan" necks are considered elegant in many cultures, including the fashion world. Models are advised not to hide this quality, even to enhance it with jewelry (earrings, necklaces, chokers), so we as pinup artists should do likewise.
The head isn't a helium balloon; it has weight. Therefore, the neck is never a rigid, up-and-down lollipop stick, but a natural continuation of the 's' curve of the spine. It's thinner at the base and thicker near the ears, only appearing otherwise because of the sloping trapezius muscles that flank it. Note that the area beneath the jaw is not indented. Rather, it has a slight thickness.
The neck's swiveling, twisting array of motion should be employed to create large (lg) and small (sm) negative areas to either side of the head. Even if the difference in size is negligible, this will do wonders in loosening up the pose, and introducing variety.
The mastoid muscles in front and the trapezius muscles in back are really the only ones that require any sort of definition. Avoid drawing adams apples, veins, tendons or any excess wrinkles resulting from a pinch, as these will make the neck look sinewy and grotesque. The severity of the neck pit and collarbones will be dependant on the pose and angle you've chosen, and how volumptous your subject is. Err on the side of thin necks vs. thick ones, as the latter are a decidedly manly trait.
