Cut ½- to 1-inch of stem from the bottom of each flower stem and greenery stem. Immediately place the cut ends in a container of water so the bottom one-third of the stems are covered with water. Allow the flowers and greenery to hydrate for at least three hours.
Clean the vase with dishwashing soap and water. Fill the vase three-fourths full of clean water.
Place the greenery into the vase first. You may need to cut the stems of the greenery to make the greenery form a full, even shape. Also, there should be enough greenery in the vase to hold the stems upright. If the vase will be viewed from one side, make the greenery higher in the back. If it is to be viewed for all sides, make the greenery higher in the middle and lower on the sides.
Place the tallest flowers in the vase first. The tallest flowers should be one and one-half times the height of the vase. For example, if the vase is 12 inches high, the tallest flowers should be 30 inches tall. This is the professional florist method of making the floral arrangement look balanced with the vase.
Add shorter and smaller flowers until the flower arrangement appears well-balanced. Do not crowd the flowers or attempt to fill in every space with flowers. The flowers should be evenly spaced.
Add more greenery and smaller filler flowers as needed to complete the arrangement and give it a finished and balanced appearance.