General guidelines for stretching:

Before stretching, you should be warmed up by taking a brisk walk, jogging lightly, performing jumping jacks, or doing any form of aerobic exercise that warms the body. Stretch all your muscles, but pay close attention to those muscles that you will be using most during your sport or exercise, or that you used most during a sport or exercise if you are stretching after a workout. Hold each stretch for ten to twenty seconds. Repeat the stretch two to three times in succession or as many times as you feel are necessary, and do not move on to the next stretch until completion. Stretch to the point just before discomfort, and the feeling of initial tightness will diminish as the stretch is held. If tightness intensifies or you feel pain, release the stretch. Take deep breaths and breathe out into your stretch, but never hold your breath. Shake out your limbs between each stretch. Ease in and out of each stretch slowly. Do not bounce during your stretches. Perform your stretching routine at least three times a week, but ideally five times per week. The more you perform your routine, the easier it will become. It is important to stay active!

Benefits of stretching:

Stretching will increase your flexibility and range of motion. It will reduce your risk of injury during everyday activities as well as during exercise. Stretching relieves muscle tightness, soreness, and stiffness. It will improve posture, help with balance, and can reduce chronic pain. It will reduce lactic acid buildup and will increase blood flow to the muscles being used. Lactic acid is a byproduct of exercise and can cause discomfort and soreness. Stretching after an intense exercise or physical activity can reduce muscle soreness, which is called delayed onset muscle soreness (DOMS).