I had a trainer who taught me Active Isolated Stretching (AIS) which involves keeping the muscles you want more flexible in motion, 5-10 reps of 2 seconds duration. With a static stretch, you hold the stretch for 15-30 seconds. With AIS, you hold the stretch 2-3 seconds, but move in and out of the stretch position 5-10 times. I find this to take slightly longer than static stretching, but with much better results. I had problems with mobility when I weighed a 120lbs more. My trainer got me moving by stretching my hip rotators. A lot of injury problems I had in my back were related to hip inflexibility in this manner. I have lost a great deal of weight (weight loss surgery) since then; I continue to work on flexibility while I increase my strength and cardiovascular fitness. I do about 30-45 minutes of floor work 3-4x/week, about 25 minutes of which is stretching, the rest is core strengthening. Yoga and Pilates are also good options. Others here have experience with those. I've just heard good things from others.