My personal best was 17'5 at the golden west invitational in'87. My athletes at Galt High School in Galt, CA, are currently averageing 15'0. I also coached at IU for 3 years and had a 18'6 vaulter. A good plant followed by a good swing up. Having the pole planted in the corner of the box.
Speed also is a key to a good plant.
Good leg extension and a great plant. Being totally inverted and having a clean rotation off the pole. Work in the weight room 3 days a week and do pole vault drills 3 days a week. When I was in high school and college I loved to do swing ups off the bleachers on to the pits. Don't goof around on the mats and stretch out.