Cut the flowers from the plants in the garden using the sharpest knife or pruning clippers you can find. The cut should be as clean as possible. Avoid using ordinary scissors, because they will squeeze and crush the stem, rendering it incapable of absorbing moisture.
Place the fresh-cut stems from the garden directly into the pail or basin of tepid water. If you have purchased flowers, unwrap the stems and place them into the pail or basin as soon as you get them home.
Take one stem out at a time and lay it on the cutting board. Cut off the bottom 1/4- to 1/2-inch of stem with the sharp knife. Score the stems at a 45-degree angle so that more of the stem's open surface will be exposed to the water. Cut rose stems at an angle or use the knife to make several small, vertical cuts in the base of the stem.
Place the scored flower stems directly into the vase or other container as soon as the cuts are made. Leaving the freshly-cut stems out in the open air for even brief periods starts the deterioration process.