How to get clean shoulder and hip deformation, weight painting, and facial rigs?

[Mason_C]

I'm a 3D artist learning character rigging for the first time to animate my own creature designs in Blender. I've built a basic humanoid armature, but I'm running into major issues with deformation, especially around the shoulders and hips during complex poses. The mesh pinches and stretches in unnatural ways. For more experienced riggers, what are the key principles for creating clean, flexible deformation groups and weight painting? Are there specific tools or add-ons within Blender that you consider essential for efficient rigging, or is it better to master the core systems first? I'm also unsure how to approach facial rigging for subtle expressions versus more cartoony, broad movements.