Nice Excerpts include:
"The objective is to bend the pole past 90 degrees (top of pole must be at least horizontal with the runway with both hands at least level with the runway while you are still on the ground.) The longer the pole the easier this becomes so don’t expect this too soon especially with short poles."

"The jumper must let the pole do most of the work, so bend it and let it throw you over the bar. The bigger the pole the more throw you will get at the top. The ideal position of the hands at your plant should have their front hand higher than their back hand. This can only be accomplished when they bend the pole over 90 degrees."
"[How does the vaulter bend the pole?]They simply keep the pole away from them as they run under the pole while planting. "