Put flowers in water as soon as you get them home. Fill buckets with tepid water, add floral preservative, and then add flowers.
Cut an inch off the stems using a sharp knife, especially if the flowers will sit a while before being arranged. The fresh cut will help the stems absorb water better.
Warm water helps tightly closed flower heads, such as roses or ranunculus, to open fully. Leave them in water for a day or two before using them.
Use florist's foam to keep flowers in place and constantly hydrated so they last longer. Soak the foam for 15 minutes before cutting it to fit the container. Water the foam every couple of days.
Recut stems just before adding them to the arrangement. Strip off any leaves that fall below the water line.
Add large, heavy flowers first turning the arrangement as you work to ensure even placement on all sides. Fill in with smaller, airier blooms, and leave enough space between the stems so individual flowers have room to shine. Include flowers with various shapes and stem lengths.
Make your bouquet taller than its container by about one and a half times. Also, make the width balance the height.
Mix in different textures for a monochromatic arrangement that's interesting to look at.
Save larger leaves and stems with leaves on them to fill in around the flowers. Drape some of the greenery over the container's rim.
Keep flowers away from sunlight and heating vents. Recut stems and add water often.