Here is an easy and inexpensive tip that I use often.
Mix ½ – 1 teaspoon of vodka or clear spirit to 16oz of water for the vase.
Cut the stems at an angle to help with absorption.
I recently bought a bouquet of Hydrangeas that wilted severely. Instead of throwing them out, I cut the stems at an angle and mixed in a teaspoon of vodka (not the good stuff) to the water in my vase. In a matter of hours, they completely recovered.