1. Try to pick them early in the morning when they are still cool. Not during the heat of the day.
2. Be sure to strip off leaves and anything that will go beneath the water line, but keep the leaves above the water line. Note: Only the freshly cut bottom of the stems, not the shaft, absorbs water. Cut at an angle so more surface is exposed.
2. Change the water every other day and also cut of ¼ inch of the stem.
3. Never put the flower arrangement, near a heat source, like the top of the TV, or in direct sunlight.