And while there has been a long debate over if stretching before or after exercise is better. Stretching before exercise is recommended for vigorous activity, to prepare your muscles to move. You'll find a better range of motion or movement if you stretch before hard, because your body is more prepared and has been warmed up for activity.
Afterwards stretching is also recommended to help work as a warm down, and to move the lactic acid you build during activity out of the muscles.
An article from the department of kinesiology and health at Georgia State University says that age in particular effects your range of motion the most. Daily activities are influenced by our flexability. Regularly stretching can help lengthen and restore muscles back to their younger form. The GSU article says stretching can help
relax your mind and tune up your body,The GSU article, including a list with pictures and descriptions of some helpful daily stretches is available here.
preserve range of motion
maintain flexibility
prevent injury during exercise
prepare muscles for vigorous activity
develop body awareness
promote circulation
For length of stretching, this Q&A on the Runners World website has a good response to the amount of time you should promote to working your muscle flexibility. In general, about 30 seconds holding for each stretch is best.
Slowly moving forward to a steady hold is ok, but try not to bounce or move around too much while stretching as you could do more damage to your muscles than good.
For more information on stretching and flexibility, here is a great videojug video on stretches to improve flexibility.
