What is the best method for preserving cut flowers in a vase?

What is the best method for preserving cut flowers in a vase? I┬┤ve heard of preserving cut flowers in water mixed with a lime carbonated soft drink

The secret to keeping cut flowers from wilting is to give them a constant supply of water. The first rule is to cut in the early morning, and take only the freshest, just barely opened flowers. If you can place cut flowers into a container of water immediately after cutting, you will keep the vascular system within the stem working in an upward direction. When you take the stems out of water, air can clog the cells and can stop the capillary action. Place the stems into a container filled with a mixture of 1 teaspoon bleach and 1 tablespoon of sugar stirred into 1 gallon of water. The acid slows bacterial growth and the sugar provides nutrients. Change the solution every three days to help prolong the blooming time. You can use a soft drink, as it contains both acid and sugar.