Static Stretching is used to stretch a muscle while the body is at rest. It is comprised of various techniques that gradually lengthen the muscle to an elongated position (to the point of discomfort) and holding that position for 30+ seconds.
Statically stretching a muscle before training has been shown to interfere with performance and augments the joint and can promote instability in the joint making the person more susceptible to injury.
However stretching after a training session as part of a cool down to help improve flexibility can lengthen a tightened muscle. It can also help relive stress and tension.
Static Stretching should be done NOT BEFORE a training session but AFTER!
For your warm up I would start with Dynamic Stretching, stay tuned blog post to following on Dynamic Stretching.