The Quad Stretch
A posterior driven gait requires that you have some amount of hip extension available. However, many of us lack the range of motion in the hip necessary due to the frequency of time we spend in hip flexion (think how often your thighs are in front of the hips). For this reason, it's important to "uncast" our hips from the position of our chairs, etc. by standing and stretching those hip flexors as much as possible. One fantastic stretch is the classic "runner's" stretch or quad stretch. Simply stand on one leg and grab the ankle of the other leg. You can use this stretch as a way to assess how much tension you carry in the front of the thighs in relation to how much strength you have in the back of the thighs:
Notice how you have to "contort" your body to grab that ankle. Did you have to twist the torso, flex the thigh forward and out to the side, or move really fast?
Try to move slowly and keep the thighs close together and see if you are able to grab the ankle.
If the tension in your thigh is too great, just hold the ankle (you can even use a strap for this) and do the stretch often while also practicing the quad release (relax your kneecaps down).
As the strength in the back of the leg becomes more balanced with the relaxation of the front of the leg, you'll really begin to feel the effect of the posterior driven gait.