To help increase endurance and stamina, I like to sprint or run pretty fast. For endurance, I run at a fast pace, but one that I can keep up for two or three miles. This should be exhausting. For stamina increase, I sprint as fast as I can for as long as I can, usually right after a fat-burning workout. Burning excess fat will improve flexibility and muscle tone, while a stronger cardiovascular system will allow longer periods of fast sparring, while forms will be lower, faster, and more powerful, with less exhaustion.
Strength training is an important aspect of conditioning.
Weight lifting is the most popular form, though strength conditioning encompasses any exercise performed with resistance applied to one or more muscle groups. Even riding a bike on a high level will stress the quadriceps and calf muscles as well as burn fat and benefit the cardiovascular system. Weightlifting, however, is so popular not only because of the western conception that bigger muscles are better, but also because proper training can produce good results. Eating right provides the energy to practice kung fu intensely, and helps speed workout recovery. It benefits the circulatory system to eat right, providing a shot at the longevity that Shaolin masters of the past are so renown for.