Floral bouquets usually come with a packet of preservative. This is very critical to making the bouquet last as long as possible. Bleach can be used as a temporary preservative, but is not nearly as helpful. Fill a vase to the rim with warm water, empty the contents of a preservative packet in the water and mix well. Pour some of the solution into a large bowl.
Air can clog the stem of flowers when the stem is trimmed.
Do not use scissors to trim the stem. They can crush it. Trim the flowers with Oriental shears or a sharp knife. Make a nice, clean cut. Remove leaves from the parts of the stems that will be underwater.