I actually dissent. Having run for forty years, i believe that running does not have to cause injury if there is no intenal pathology. I would start slow with a walk/ run combo. I would then gradually increase to 20-30 minutes running 3-5 times per week i think the duration or distance covered is more important than the speed. Oviously the speed will naturally increase with a training effect.
Distance. Depending on your age & physical condition, walking may be a better choice as there is less impact on ankles, knees, & hips. Distance may be less important that the speed with which you cover the distance. Try a mile at normal pace; work to decrease the time to do the mile. Pool aerobics are another low impact, healthful exercise.