Flexibility refers to the set range of motion your muscles have. This range of motion is within our control, although it does have a natural 'set' point. It is through proper stretching exercises that we can reset the body's natural set points. Each time we stretch properly and consistently, we push the set point farther. The muscles acclimate to the more elongated positions over time, increasing our flexibility.
Do not believe the myth that flexibility comes at the expense of strength. In fact, a good stretching routine in conjunction with a strength training program actually increases the muscles usable strength, giving better results than a strength training program alone would otherwise give you. Think about gymnasts, who are about as flexible as you can get, and also have superior core body strength which allows them to manipulate their body weight through full ranges of motion.
Despite what you might have heard, it is the muscles that do the stretching. Tendons and ligaments aren't flexible by nature, and care must be taken to not damage them. So a key to proper stretching is an awareness of pain. Slight pain (i.e. a tingling sensation ) is acceptable when stretching, but any sensation of pain beyond that indicates you are stretching too hard, tearing the muscles and perhaps damaging your tendons, ligaments and joints. So stretch safely and slowly. Remember, this is not a contest. You are only trying to be better than the day or week before, not better than the person in your class who apparently sits in the floor in a full side split effortlessly.
Stretching cold is always a bad idea. It in fact weakens the muscles by depleting their contracting strength and can severely tear them. Always warm up before you stretch. Of course, the question becomes what is a sufficient warm up. This would include relaxed joint manipulations followed by about five to ten minutes of simple exercise - think light jogging, jumping jacks, etc. The idea is to warm up the muscles of the body and raise your core body temperature. It is well worth taking the extra time to warm up before stretching, as otherwise the damage you will do by stretching cold will set you back further.
The best time to stretch for gains in flexibility is after intense physical exercise. Again, take the time after a hard Capoeira class, or an intense workout at the gym and stretch those muscles! At this point the muscles can be stretched, as they are warmed up and fatigued. It is easier to 'reset' a fatigued muscle to a longer length. Stretching after an intense workout also will help alleviate muscle soreness the next day by flushing out lactic acid and other exercise by products that collect in the muscle tissues. Also remember to drink plenty of water.
A good stretching regimen should also include an early morning stretching session every day. This should include a general warm up and a complete, but light, stretching routine. The idea behind the morning stretch is to reinforce the muscles 'memory' to longer and longer lengths, and to keep the muscles supple for the day. Light morning stretching is not the time to increase your flexible range, but rather to reinforce the gains already made.
Incorporate both static and dynamic stretching into your program. Again, always do a warm up, do static stretches first, followed by dynamic stretches. I can assume that we are familiar with a number of basic static stretches. Dynamic stretches are exercises which take the muscles through their entire range of motion, without adding too much effort. Think of swinging kicks, arms, torso, etc. here. The idea is not to force your muscles beyond the comfortable range, but to take them dynamically through there whole range of motion without using force. You are not trying to power your kicks higher for example. Always do the static stretches first though!
With static stretching, holding a position for ten to twenty second is usually sufficient, and studies have shown that one or two repetitions of a given stretch are sufficient per session for increasing flexibility. More than two reps does not dramatically increase results. A good thing to remember when trying to be as efficient as possible with your time and your program. For the dynamic stretches, perhaps two sets of ten reps per exercise should work. Another key is the order in which you stretch those muscles. People often just sit on the floor in a saddle stretch and consider themselves stretched! Here is the proper order for stretching the major muscle groups of the body:
Lower Back Stretch - Lying on the floor bring both knees up to the chest and hold.
Oblique Stretch - Lying on the floor, bend knees and place feet flat on floor. Bring both knees and hip to one side. Hold stretch. Repeat with opposite side.
Neck Stretch - Gently pull head down in front using the hand and gently pull neck to the side.
Forearm and Wrist Stretch - Start by kneeling with your palms flat and your fingers pointing back toward your knees. Slowly lean back keeping your palms flat on the floor until you feel a stretch in your wrists and forearms.
Tricep Stretch - Bend right arm at elbow joint, lift arm next to your head. Position right fingers so they touch the shoulder blade area. Place left arm across top of head, and place left hand on the right elbow to gently support the arm during this stretch.
Chest Stretch - Clasp your hands behind your back with your palms facing up. Pull your hands down and press your shoulder blades together. Your chest should stick out. You should feel the stretch in your upper arms and chest.
Buttock Stretch -Lying on your back, legs bent. Lift your leg & let the knee fall out to the side so that you are able to place your ankle on top of the opposite knee. Hold the knee & ankle of the raised leg & lift both legs as a unit, bringing them towards your chest to create a stretch in the buttock. Keep your back on the floor. Repeat on the other side.
Groin Stretch - Butterfly stretch sitting on the floor with feet together gently press elbows on knees, hands on ankles.
Thigh Stretch - While standing, grab ankle and point knee straight down. This can also be done lying on the side.
Calf Stretch - Lunge position, front leg slightly bent has knee directly over ankle, back leg straight with heel down on floor, both toes are facing forward. Shift body weight forward over the front foot.
Shin Stretch - Lie on one side. Grasp top forefoot behind. Pull forefoot to lower back. Hold stretch for 20 seconds. Repeat with opposite foot.
Hamstring Stretch - Sitting with legs in a pike or V seat position lean forward with a straight back and hold towards feet.
Instep Stretch - Facing a wall, put the ball of one foot up against the wall Bend the knee and lean toward the wall, keeping the heel of the front foot down Repeat with the opposite side.
Stretching in this order assures the optimum and most efficient stretching of the muscles. For example to get the best possible stretch from the hamstrings it's important that the muscle groups that support them (i.e. the buttocks, lower back, calves and thighs) are already stretched. The above order is an optimum order for getting the most out of a full body stretching routine. The same order exists for both static and dynamic stretching portions of your training.
Working towards the Splits Stretching exercises: http://people.bath.ac.uk/masrjb/Stretch/stretching_7.html#SEC73
Conditioning Exercises for Capoeira. http://video.google.co.uk/videoplay?docid=3274574255674264038&q=capoeira&total=27117&start=20&num=10&so=0&type=search&plindex=2