Take the bouquet of flowers out of the wrapper that they came in. Cut the stems of the flowers on a diagonal. This will optimize the surface space that draws in fresh water for them.
Crush an over the counter aspirin and place it in the bottom of the vase. Arrange the bouquet of flowers in the vase.
Fill the vase with room temperature water to within an inch of the top.
Remove the flowers from the vase after a week. Dump the water out of the vase and wash it out thoroughly. Make sure that you rinse out all of the soap in the vase.
Cut the flowers a half inch from the original cut, on the diagonal. This will give the flowers a fresh cut in which to take in water. Crush an aspirin and place it in the vase and rearrange the flowers. Fill the vase with room temperature water.