What do your clients or athletes have in common?  I will give you a hint.  Do the words shoulder, chest, hamstrings, and hips help?  They are tight!  On just about everyone these areas are particularly tight, which can lead to imbalances in your muscle groups and ultimately injuries.   Stretching needs to be individualized just like the strength and conditioning programs we design.  Unless you tailor your flexibility training to the strengths and weaknesses of your clients and athletes, you may stretch already overstretched muscles and miss areas that need more focused training.  Pay particular attention to older adults, pregnant women, and people with injuries.  They may need special precautions when involved in a flexibility program.